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1. OpenSSH 10.6 Oct 6, 2026 · issue 096

   OpenSSH 10.6 adds post-quantumpost-quantumCryptography designed to stay secure against a large quantum computer, which could break today's RSA and elliptic-curve keys. NIST standardized the first algorithms in 2024 as ML-KEM, ML-DSA and SLH-DSA. signatures, WarnWeakCrypto for sshd, AgentSocketPath, FIDO PIN-skip -P, and fractional ChannelTimeout.⁠︀︄︇︀︅︉︀︅︀︀︃︀︀︅︅︀︅︊︀︄︆︀︃︄⁠

   └──▷ USE IT
   Warn sshd operators when connecting clients negotiate non-post-quantum-safequantum-safeCryptography designed to stay secure against a large quantum computer, which could break today's RSA and elliptic-curve keys. NIST standardized the first algorithms in 2024 as ML-KEM, ML-DSA and SLH-DSA. key exchange, while also routing agent sockets to a per-user path instead of a shared directory.
   /etc/ssh/sshd_config copy

   WarnWeakCrypto yes
   AgentSocketPath user:.ssh/agent

   Allow a larger agent key inventory to be probed before the server disconnects — useful when many keys are loaded in ssh-agent.
   /etc/ssh/sshd_config copy

   PubkeyOptions max-pk-ok:20

   Enable TCPTCPA network protocol that delivers a reliable, ordered stream of bytes between two endpoints. It detects lost data and retransmits it. keepalives on both the main SSH connection and any forwarding sockets to detect dead tunnels faster.
   copy

   $ ssh -o TCPKeepAlive=all user@bastion

   • Adds WarnWeakCrypto option to sshd_config(5), enabled by default, logging when a client uses a key-agreement scheme that is not post-quantum safe (previously client-only).⁠︀︄︇︀︅︉︀︅︀︀︃︀︀︅︅︀︅︊︀︄︆︀︃︄⁠
   • Adds AgentSocketPath option to sshd_config(5) to control the location of $SSH_AUTH_SOCK for agent forwarding, supporting user:<path> (e.g. user:.ssh/agent) and shared:<path> (e.g. shared:/tmp) directory styles; sockets in shared directories are created inside a subdirectory with a randomised name.
   • Adds PubkeyOptions max-pk-ok:nnnn to let a configurable number of PK_OK public-key probe tests proceed without counting against MaxAuthTries, defaulting to 6, allowing more keys in ssh-agent or on disk to be checked before disconnection.
   • Extends TCPKeepAlive in ssh(1) and sshd(8) to accept a new all value that additionally enables keepalives on forwarding sockets, not only the main connection socket (yes/transport retains the previous behaviour).
   • Enables hybrid post-quantum ssh-mldsa44-ed25519 signature algorithm across all components; keys generated with the previous experimental (@openssh.com-suffixed) implementation must be regenerated.

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   • Adds -A flag to ssh-agent(1) to specify agent socket directories, accepting the same user: and shared: styles as the new sshd AgentSocketPath option.
   • Adds -P flag to ssh-add(1) to skip PIN entry for FIDO and PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. tokens that do not require it.
   • Adds hexdump key export mode to ssh-keygen(1) (e.g. ssh-keygen -em hexdump -f /key) that dumps the SSH wire-formatted key blob in hex format.
   • Adds -p flag to sftp(1) mkdir/lmkdir subcommands to create parent directories as needed, analogous to mkdir -p, without erroring on pre-existing directories.
   • Allows ChannelTimeout in ssh(1) and sshd(8) to accept fractional-second timeout values.
   • Preserves user-verification (PIN or biometric) requirements for resident FIDO keys loaded from a token by checking the credential's credProtect policy in ssh-keygen(1) and ssh-add(1).
   • Includes local and remote SSH version strings in the ~I connection information display in ssh(1).
   • Adds WarnWeakCrypto option to sshd_config(5), enabled by default, logging when a client uses a key-agreement scheme that is not post-quantum safe (previously client-only).⁠︀︄︇︀︅︉︀︅︀︀︃︀︀︅︅︀︅︊︀︄︆︀︃︄⁠
   • Adds AgentSocketPath option to sshd_config(5) to control the location of $SSH_AUTH_SOCK for agent forwarding, supporting user:<path> (e.g. user:.ssh/agent) and shared:<path> (e.g. shared:/tmp) directory styles; sockets in shared directories are created inside a subdirectory with a randomised name.
   • Adds PubkeyOptions max-pk-ok:nnnn to let a configurable number of PK_OK public-key probe tests proceed without counting against MaxAuthTries, defaulting to 6, allowing more keys in ssh-agent or on disk to be checked before disconnection.
   • Enables hybrid post-quantum ssh-mldsa44-ed25519 signature algorithm across all components; keys generated with the previous experimental (@openssh.com-suffixed) implementation must be regenerated.
   • Adds -A flag to ssh-agent(1) to specify agent socket directories, accepting the same user: and shared: styles as the new sshd AgentSocketPath option.

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   • Adds -P flag to ssh-add(1) to skip PIN entry for FIDO and PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. tokens that do not require it.
   • Adds hexdump key export mode to ssh-keygen(1) (e.g. ssh-keygen -em hexdump -f /key) that dumps the SSH wire-formatted key blob in hex format.
   • Adds -p flag to sftp(1) mkdir/lmkdir subcommands to create parent directories as needed, analogous to mkdir -p, without erroring on pre-existing directories.

   4 more in Everything

   └──▷ BREAKING ON UPGRADE

   • !The ssh-mldsa44-ed25519 algorithm no longer uses the @openssh.com vendor extension suffix; keys generated with the previous experimental implementation must be regenerated and/or removed.
   • !Compression is less effective: the LZ77LZ77A lossless compression algorithm that replaces repeated byte sequences with back-references to earlier occurrences in a sliding window buffer, forming the basis of zlib, gzip, and deflate. dictionary coder is disabled in ssh(1) and sshd(8) to mitigate a cross-channel plaintext-recovery side-channel.
   • !ssh(1) now rejects command-line usernames containing $ or \ characters; usernames specified via the User directive in config files are not affected.
   • !On platforms that do not support file descriptor passing and require root for PTY allocation (e.g. QNX 6, SCO OpenServer 5, or builds with --disable-fd-passing), GatewayPorts and StreamLocalForwarding are forcibly disabled.
   • !The scp -R flag now emits a deprecation warning to standard error; it will be ignored in a future release.
   • !On OS X SDK >= 27, sshd(8) sandboxingsandboxingRunning code inside a restricted environment that limits what it can access or change. The isolation reduces the impact of mistakes or untrusted code, depending on the sandbox's controls. is no longer supported as the required API has been removed.
2. changelog Aug 11, 2026 · issue 042

   OpenSSH 10.5 adds ssh -Z key-preview mode, FIDO flag editing on passphrase reset, and smarter FIDO key ordering for pubkey auth.

   └──▷ TRY IT
   Preview exactly which keys SSH will offer — and in what order — before connecting to a host, useful for debugging pubkey auth failures.
   copy

   $ ssh -Z user@host

   • Adds ssh -Z user@host mode that prints the public keys that will be tried for pubkey authentication, in the order they will be used.
   • Adds ability to set or clear the touch-required and verify-required flags on FIDO private keys when resetting a private key's passphrase.
   • Reorders FIDO key trials during pubkey authentication to prefer low-friction keys (no user presence required) before high-friction keys (PIN or biometric verification).
   • Makes ssh-keyscan banner reading non-blocking so a stuck server no longer stalls a multi-host keyscan.
   • Re-allows PAMServiceName inside a Match block in sshd_config (had been incorrectly disabled in 10.4).

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   • Allows ChannelTimeout and RekeyLimit to be set inside sshd_config Match blocks.
   • Moves public key type check against allowed algorithms to before key parsing, reducing pre-authentication attack surfaceattack surfaceThe exposed systems, interfaces and access points an attacker could try to use. It includes internet-facing services as well as identities, software and other reachable resources..

   7 details in Everything

   └──▷ BREAKING ON UPGRADE

   • !Portable OpenSSH now requires ECC (Elliptic Curve Cryptography) support in libcrypto, including support for the NISTP521 curve; builds against a libcrypto without ECC will fail. The --without-openssl build configuration is not affected.
3. OpenSSH 10.5 seen Aug 11, 2026 · issue 042

   OpenSSH 10.5 adds FIDO key flag editing, smart pubkey ordering, and a new ssh -Z auth-key inspection mode

   └──▷ TRY IT
   Inspect which keys ssh will present for public key authentication and in what order, before actually connecting — useful for diagnosing auth failures or unexpected key selection.
   copy

   $ ssh -Z user@host

   • New ssh -Z user@host mode prints the public keys that will be tried during authentication, in the exact order they will be attempted.
   • Adds ability in ssh-keygen(1) to set or clear the touch-required and verify-required flags on FIDO private keys when resetting a passphrase.
   • ssh(1) now tries FIDO keys that require no user presence first, and FIDO keys requiring PIN or biometric verification last, reducing unnecessary friction during pubkey authentication.
   • sshd(8) now uses setproctitle(3) to label the sshd-session process when acting as a post-authentication monitor, improving process visibility.

   4 details in Everything

   └──▷ BREAKING ON UPGRADE

   • !Portable OpenSSH now requires ECC (Elliptic Curve Cryptography) support — including the NISTP521 curve — in libcrypto; builds against a libcrypto without ECC will fail. The --without-openssl build configuration is not affected.
4. OpenSSH 10.4 Jul 6, 2026 · release notes

   OpenSSH 10.4 adds experimental ML-DSAML-DSANIST's main post-quantum digital signature standard (FIPS 204), formerly Dilithium. It is the planned replacement for RSA and ECDSA signatures on certificates and code. 44/Ed25519Ed25519A fast elliptic-curve signature scheme with small keys, the default for new SSH keys and common in code signing. It is not quantum-safe. composite post-quantumpost-quantumCryptography designed to stay secure against a large quantum computer, which could break today's RSA and elliptic-curve keys. NIST standardized the first algorithms in 2024 as ML-KEM, ML-DSA and SLH-DSA. signatures and NFA-based wildcard matching

   └──▷ TRY IT
   Generate a composite post-quantum key for testing.
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   $ ssh-keygen -t mldsa44-ed25519

   Configure a server to accept the new post-quantum algorithm.
   text copy

   HostKeyAlgorithms mldsa44-ed25519
   PubkeyAcceptedAlgorithms mldsa44-ed25519

   Connect using the new post-quantum signature scheme.
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   $ ssh -o HostKeyAlgorithms=mldsa44-ed25519 user@host

   • Adds mldsa44-ed25519 as a new key type for HostKeyAlgorithms and PubkeyAcceptedAlgorithms to enable experimental post-quantum signature support.
   • Generates composite post-quantum keys using the new ssh-keygen -t mldsa44-ed25519 subcommand.

   2 details in Everything

   └──▷ BREAKING ON UPGRADE

   • !sshd -G now writes directives in mixed case (e.g., PubkeyAuthentication) instead of only lower-case names.
   • !On Linux with seccomp sandbox enabled, sshd(8) fails fatally if SECCOMP or NO_NEW_PRIVS cannot be enabled, instead of logging and continuing.
5. OpenSSH 9.9 seen Jun 29, 2026 · issue 001

   OpenSSH 9.9 defaults to ML-KEMML-KEMNIST's post-quantum key-exchange standard (FIPS 203), formerly Kyber. Two parties use it to agree on a shared secret, usually alongside X25519 in a hybrid TLS handshake. post-quantum key exchangepost-quantum key exchangeA cryptographic handshake algorithm designed to resist attacks from quantum computers, using math problems like lattices that quantum algorithms cannot efficiently solve, letting tools stay secure against future quantum-capable adversaries., drops DSA key support, and adds new signing tools.

   └──▷ TRY IT
   Verify a principal name appears in your allowed-signers file before trusting a signed artifact — useful in CI pipelines.
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   $ ssh-keygen -Y match-principals -I alice@example.com -f /etc/ssh/allowed_signers

   Harden an sshd deployment by killing idle SSH channels after 5 minutes and unused connections after 10 minutes.
   ini copy

   ChannelTimeout session:5m
   UnusedConnectionTimeout 10m

   • Adds mlkem768x25519-sha256 hybrid post-quantumpost-quantumCryptography designed to stay secure against a large quantum computer, which could break today's RSA and elliptic-curve keys. NIST standardized the first algorithms in 2024 as ML-KEM, ML-DSA and SLH-DSA. key exchange as the new default, replacing sntrup761x25519-sha512.
   • Removes DSA key support entirely — DSA host keys and user keys are no longer accepted (breaking change practitioners must act on).
   • Adds ssh-keygen -Y match-principals subcommand to test whether a principal is listed in an allowed-signers file.
   • Adds support for reading the list of authorized principals from a file via AuthorizedPrincipalsFile in combination with cert-based auth.
   • Enables ChannelTimeout and UnusedConnectionTimeout directives in sshd to terminate idle channels and unused connections automatically.

   5 details in Everything

6. OpenSSH 10.3 Apr 2, 2026 · release notes

   OpenSSH 10.3 adds agent query extension, multi-file key directives, connection info commands, and ed25519/PKCS8 support.

   └──▷ TRY IT
   Query the local SSH agent to see which protocol extensions it supports before scripting agent interactions.
   copy

   $ ssh-add -Q

   Inspect open channels on an existing multiplexed session to troubleshoot connection state without opening a new shell.
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   $ ssh -O channels user@host

   • Add ssh-add -Q to query the SSH agent's protocol extensions via the draft-ietf-sshm-ssh-agent query extension
   • Add -J/ProxyJump user and host name validation on the command line for ssh(1)
   • Support multiple files in the sshd_config RevokedKeys directive
   • Add ~I escape option to show current SSH connection information
   • Add ssh -O conninfo user@host multiplexing subcommand to display connection info

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   • Add ssh -O channels user@host multiplexing subcommand to list open channels
   • Add invaliduser penalty option to PerSourcePenalties in sshd_config
   • Add GSSAPIDelegateCredentials server option in sshd_config
   • Support VA DSCP codepoint in the IPQoS directive for ssh(1) and sshd(8)
   • Convert PerSourcePenalties to floating point time for sub-second granularity

   10 details in Everything

   └──▷ BREAKING ON UPGRADE

   • !Removed bug compatibility for SSH implementations that do not support rekeying; connections with such peers will fail during transport rekeying.
   • !Changed handling of certificates with an empty principals section via authorized_keys principals="" option: previously matched any principal (wildcard), now matches never, preventing accidental wildcard authentication.
   • !Wildcard characters in certificate principals are now consistently implemented for host certificates and unsupported for user certificates.
7. OpenSSH 10.1 Oct 6, 2025 · release notes

   OpenSSH 10.1 adds RefuseConnection, -N to ssh-add, PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. ed25519, and improved DSCP handling

   └──▷ USE IT
   Refuse a connection immediately based on host matching in config.
   text copy

   Host deprecated-server
       RefuseConnection "Use mirror-host instead"

   Suppress stale socket cleanup when starting a new agent.
   copy

   $ ssh-agent -U

   • Adds RefuseConnection ssh_config option for early connection termination in config files.
   • Adds ssh-add -N option to disable automatic certificate expiry grace periods.
   • Supports ed25519 keys on PKCS#11 tokens via ssh(1) and ssh-agent(1).
   • Adds WarnWeakCrypto ssh_config option to control warnings for non-post-quantum key exchangepost-quantum key exchangeA cryptographic handshake algorithm designed to resist attacks from quantum computers, using math problems like lattices that quantum algorithms cannot efficiently solve, letting tools stay secure against future quantum-capable adversaries. algorithms.
   • Moves default ssh-agent socket path from /tmp to $HOME/.ssh/agent with new flags -U, -u, -uu, and -T.

   5 details in Everything

8. OpenSSH 10.0 Apr 9, 2025 · release notes

   OpenSSH 10.0 adds post-quantumpost-quantumCryptography designed to stay secure against a large quantum computer, which could break today's RSA and elliptic-curve keys. NIST standardized the first algorithms in 2024 as ML-KEM, ML-DSA and SLH-DSA. KEX, new ssh_config Match directives, scoped key deletion and glob-based auth file matching.

   • ssh(1) now defaults to the hybrid post-quantum mlkem768x25519-sha256 key agreement algorithm for connections.
   • Adds support for Match version, Match sessiontype, and Match command in ssh_config for granular conditional configuration.
   • Adds -Owebsafe-allow=... option to ssh-agent(1) to override the default FIDO application ID allow-list.
   • sshd(8) now disables finite field (modp) Diffie-Hellman key exchange methods from KEXAlgorithms by default, keeping only Elliptic Curve and Post-Quantum options.
   • Adds glob pattern support to AuthorizedKeysFile and AuthorizedPrincipalsFile in sshd_config via glob(3).

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   • ssh-agent(1) now deletes all loaded keys when signaled with SIGUSR1, allowing key deletion without $SSH_AUTH_SOCK.
   • Adds SetEnv directive support for %-tokens and environment variable expansion in ssh_config.

   7 details in Everything

   └──▷ BREAKING ON UPGRADE

   • !Removal of the DSA signature algorithm support (completing deprecation started in 2015).
   • !sshd(8) removes finite field (modp) Diffie-Hellman key exchange from default KEXAlgorithms, which may cause connections to older servers or clients relying on modp to fail.
   • !The version string is now SSH-2.0-OpenSSH_10.0; scripts matching OpenSSH_1* may misidentify the version.
9. OpenSSH 9.9 Sep 19, 2024 · release notes

   OpenSSH 9.9 adds ML-KEMML-KEMNIST's post-quantum key-exchange standard (FIPS 203), formerly Kyber. Two parties use it to agree on a shared secret, usually alongside X25519 in a hybrid TLS handshake. post-quantumpost-quantumCryptography designed to stay secure against a large quantum computer, which could break today's RSA and elliptic-curve keys. NIST standardized the first algorithms in 2024 as ML-KEM, ML-DSA and SLH-DSA. KEX, RefuseConnection, invalid-user Match, env expansion in Include, and core dump protection

   • ssh(1), sshd(8): add mlkem768x25519-sha256 hybrid post-quantum key exchangepost-quantum key exchangeA cryptographic handshake algorithm designed to resist attacks from quantum computers, using math problems like lattices that quantum algorithms cannot efficiently solve, letting tools stay secure against future quantum-capable adversaries. algorithm (ML-KEM + X25519X25519The elliptic-curve key exchange most modern TLS, SSH and WireGuard connections use to agree on a session key. Post-quantum hybrids pair it with ML-KEM.), available by default
   • ssh_config Include directive now expands environment variables
   • sshd_config: add RefuseConnection option to terminate connections at the first authentication request
   • sshd_config PerSourcePenalties: new refuseconnection penalty class for dropped connections
   • sshd_config Match invalid-user predicate to match when the target username is not valid on the server

   +1 more show less

   • Private keys are kept out of core dump files for most of their lifespan across ssh, sshd, and ssh-agent (OpenBSD, Linux, FreeBSD)

   6 details in Everything

   └──▷ BREAKING ON UPGRADE

   • !ssh(1): removal of pre-authentication compression support
   • !Match configuration directive arguments now follow stricter shell-like quote rules; workarounds for previous simplistic quote handling may need adjustment, especially in Match exec conditions
10. OpenSSH 9.8 Jul 1, 2024 · release notes

    OpenSSH 9.8 adds PerSourcePenities for automated client blocking and splits sshd into listener/session binaries.

    └──▷ USE IT
    Block IPs that fail auth or crash sshd, exempting a trusted management range.
    text copy

    # In /etc/ssh/sshd_config:
    PerSourcePenalties yes
    PerSourcePenaltyExemptList 10.0.0.0/8

    Run ssh-keyscan silently without banner comments.
    shell copy

    ssh-keyscan -q host.example.com

    • Adds PerSourcePenalties and PerSourcePenaltyExemptList to sshd_config(5) to automatically block IP addresses that fail authentication or crash the server.
    • Splits the sshd(8) binary into a lightweight listener and a per-session sshd-session binary, removing support for disabling privilege separation or re-execution.
    • Adds -q flag to ssh-keyscan(1) to suppress hostname and banner comment lines that previously went to stderr.
    • Introduces PAMServiceName directive in sshd_config(5) (portable OpenSSH only) to explicitly set the PAMPAMBrokering administrator sessions through a gateway instead of handing out standing credentials. Access is granted for one session, to one target, and recorded. service name instead of relying on argv[0].

    4 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Support for disabling privilege separation in sshd(8) is removed; previously required code changes are no longer supported.
    • !Support for disabling re-execution of sshd(8) is removed.
    • !sshd(8) (portable OpenSSH only) no longer uses argv[0] as the PAM service name; use PAMServiceName in sshd_config(5) to configure it.
11. OpenSSH 9.7 Mar 11, 2024 · release notes

    OpenSSH 9.7 introduces ChannelTimeout global mode for idle channel management.

    └──▷ USE IT
    Automatically terminate all sessions and forwarded channels after 1 hour of total inactivity across the connection.
    shell copy

    ssh -o 'ChannelTimeout global 3600' user@host

    Build OpenSSH without DSA support by passing the appropriate flag to the configure script.
    shell copy

    ./configure --without-dsa
    make

    • Adds a new global value to the ChannelTimeout directive that closes all open channels if any remain idle for the specified duration
    • Makes DSA key support compile-time optional via WITHOUT_DSA build flag, defaulting to enabled in this release

    2 details in Everything

12. OpenSSH 9.6 Dec 18, 2023 · release notes

    OpenSSH 9.6 adds strict KEX for Terrapin defense, %j ProxyJump token, ChannelTimeout, PEM PKCS8 keys, and agent-cert PKCS11PKCS11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. loading

    └──▷ USE IT
    Terminate idle SSH channels after 10 minutes of inactivity to free up resources.
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    ssh -o ChannelTimeout=600 user@host

    Configure ProxyJump hostname expansion in ssh_config to avoid hardcoding jump hosts.
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    Host *.internal
      ProxyJump %j
      IdentityFile ~/.ssh/id_%j_ed25519

    Use a PEM PKCS8 formatted ED25519 key with ssh-agent.
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    ssh-add ~/.ssh/id_ed25519.pem

    • Adds %j token in ssh_config(5) that expands to the configured ProxyJump hostname.
    • Adds ChannelTimeout support to ssh(1) client, allowing termination of quiescent channels.
    • Adds support for reading ED25519 private keys in PEM PKCS8 format via ssh(1), sshd(8), ssh-add(1), and ssh-keygen(1).
    • Introduces a protocol extension allowing renegotiation of acceptable signature algorithms for public key authentication after the server learns the username, enabling PubkeyAcceptedAlgorithms in Match user blocks.
    • Adds an agent protocol extension to ssh-add(1) and ssh-agent(1) allowing specifying certificates when loading PKCS#11 keys.

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The RFC4254 connection/channels window limit now causes ssh(1) or sshd(8) to terminate the connection if a peer exceeds the limit by more than a small grace factor, whereas previously extra data was discarded.
    • !Invalid user or hostnames containing shell metacharacters supplied via the command-line are now banned, whereas they were previously passed through (potentially causing injection).
13. OpenSSH 9.5 Oct 4, 2023 · release notes

    OpenSSH 9.5 adds keystroke timing obfuscation and transport-level ping support.

    └──▷ USE IT
    Enable keystroke timing obfuscation in a specific SSH client session to mitigate traffic analysis attacks.
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    ssh -o ObscureKeystrokeTiming=yes target_host

    • Adds ObscureKeystrokeTiming to ssh_config to hide inter-keystroke timings for enhanced privacy against traffic analysis
    • Introduces transport-level ping capability via SSH2_MSG_PING/PONG messages in both client and server

    2 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !ssh-keygen(1) now generates Ed25519Ed25519A fast elliptic-curve signature scheme with small keys, the default for new SSH keys and common in code signing. It is not quantum-safe. keys by default, overriding previous key type defaults
    • !The Subsystem directive in sshd(8) now accurately preserves quoting of subsystem commands and arguments
14. OpenSSH 9.4 Aug 10, 2023 · release notes

    OpenSSH 9.4 adds Unix socket forwarding, Tag/Localnetwork config predicates, KRL wire format support, and new %-expansion sequences.

    └──▷ USE IT
    Use new %-expansion variables to log connection details for AuthorizedKeysCommand.
    text copy

    AuthorizedKeysCommand /usr/local/bin/keycheck %u %D %C
    AuthorizedKeysCommandUser nobody

    • ssh -W now forwards Unix Domain sockets via ProxyJump
    • Match tag predicate added to ssh_config(5) alongside the Tag directive
    • match localnetwork predicate added to Match blocks in ssh_config
    • Wire format infrastructure for KRL extensions defined in ssh-keygen, ssh-agent, and sshd
    • %D (routing domain) and %C (source/destination addresses and port numbers) %-expansion sequences added to AuthorizedPrincipalsCommand and AuthorizedKeysCommand in sshd_config

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Removes support for older versions of libcrypto; requires LibreSSL >= 3.1.0 or OpenSSL >= 1.1.1.
15. OpenSSH 9.3p2 Jul 19, 2023 · release notes

    OpenSSH 9.3p2 adds ssh-agent -P and -Oallow-remote-pkcs11 to mitigate PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. remote code executionremote code executionRemote code execution, the ability to run attacker-chosen code on another system through a vulnerability. Its impact depends on the permissions and access that code receives. via CVE-2023-38408.

    └──▷ USE IT
    Start ssh-agent with no PKCS#11 modules allowed to prevent exploitation of CVE-2023-38408 if an agent socket is forwarded.
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    ssh-agent -P ''

    Restore the previous behavior where remote clients can load PKCS#11 modules, if needed for legacy compatibility.
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    ssh-agent -Oallow-remote-pkcs11

    • Adds the -P flag to ssh-agent(1) to configure an empty or specific allowlist of PKCS#11/FIDO provider libraries, restricting which modules can be loaded during agent forwarding.

    1 detail in Everything

    └──▷ BREAKING ON UPGRADE

    • !By default, ssh-agent(8) now refuses requests to load PKCS#11 modules issued by remote clients; use -Oallow-remote-pkcs11 to restore the previous behavior.
16. OpenSSH 9.3p2(2023-07-19) Jul 19, 2023 · release notes

    OpenSSH 9.3p2 adds ssh-agent -Oallow-remote-pkcs11 and restricts remote PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. loading by default.

    • Adds -Oallow-remote-pkcs11 flag to ssh-agent to restore previous behavior of allowing remote clients to load PKCS#11 modules
    • Changes ssh-agent(1) default to refuse requests to load PKCS#11 modules issued by remote clients

    2 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The ssh-agent(8) agent now refuses requests to load PKCS#11 modules issued by remote clients by default; use the -Oallow-remote-pkcs11 flag to restore the previous behavior.
17. OpenSSH 9.3 Mar 15, 2023 · release notes

    OpenSSH 9.3 adds -G for effective config preview and -Ohashalg for SSHFP output control.

    • Adds sshd -G flag to parse and print the effective configuration without loading private keys, enabling verification by unprivileged users before key generation.

    1 detail in Everything

18. 9.2 Feb 2, 2023 · release notes

    OpenSSH 9.2 adds ChannelTimeout and UnusedConnectionTimeout directives, ~C escape command-line toggle, and -X for scp/sftp.

    └──▷ USE IT
    Automatically close SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel. channels that have been idle for more than 5 minutes in an OpenSSH server.
    text copy

    # In sshd_config:
    ChannelTimeout sftp 300m

    Scan a complete CIDRCIDRA notation for a block of IP addresses, such as 10.0.0.0/24. The number after the slash says how many leading address bits identify the network. range to collect host keys for an entire subnet.
    copy

    $ ssh-keyscan 192.168.0.0/24

    • Adds ChannelTimeout directive to sshd_config(5) for channel inactivity timeouts
    • Adds UnusedConnectionTimeout option to sshd_config to terminate idle client connections
    • Adds new EnableEscapeCommandline ssh_config option defaulting to no to control the ~C escape sequence

    3 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !EnableEscapeCommandline defaults to no, disabling the previously enabled default ~C command-line escape sequence for ssh clients.
19. 9.1 Oct 4, 2022 · release notes

    OpenSSH 9.1 adds RequiredRSASize directive, SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel. users-groups-by-id extension, and UTC date parsing

    └──▷ TRY IT
    Sign a file using an agent-hosted key, verifying it was accessed via the agent.
    copy

    $ ssh-keygen -U -Y sign -f id_rsa -n example -s signature < file.txt

    Specify a certificate validity period in UTC using the Z suffix.
    copy

    $ ssh-keygen -V 20231001000000Z:20231002000000Z

    • Adds RequiredRSASize directive to ssh_config and sshd_config to set a minimum RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it. key length.
    • Introduces users-groups-by-id@openssh.com SFTP extension for resolving UIDs/GIDs to names in directory listings.
    • Allows ssh-keygen date arguments to accept UTC suffixed with Z and hex epoch values.
    • Enables -U flag with -Y sign in ssh-keygen to require keys be hosted in an agent.

    4 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !SetEnv directives in ssh_config and sshd_config are now first-match-wins to match other directives.
    • !ssh-keygen -A will no longer generate DSA keys.
20. 9.0 Apr 8, 2022 · release notes

    OpenSSH 9.0 adds cp subcommand to sftp and defaults to hybrid NTRU+X25519X25519The elliptic-curve key exchange most modern TLS, SSH and WireGuard connections use to agree on a session key. Post-quantum hybrids pair it with ML-KEM. key exchange.

    • scp(1) defaults to the SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel. protocol instead of the legacy scp/rcp protocol, removing the need for double-quoting shell meta-characters in remote paths; use -O to revert.
    • Adds sntrup761x25519-sha512@openssh.com (hybrid Streamlined NTRU Prime + x25519) as the default key exchange method for ssh(1) and sshd(8) to mitigate 'capture now, decrypt later' attacks.
    • Adds support for the copy-data extension in sftp-server(8) to enable server-side file copying.
    • Adds a new cp command to the sftp(1) client to perform server-side file copies using the new extension.

    4 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !scp(1) no longer uses the legacy scp/rcp protocol by default; remote wildcard expansion (e.g., host:*) now happens on the client side via SFTP, so double-quoting shell meta-characters in filenames will cause transfers to fail instead of being passed through.
    • !scp(1) clients connecting to servers that do not support the expand-path@openssh.com extension cannot expand remote paths relative to other users' home directories (e.g., host:~user/file). Use -O to restore legacy behavior.
21. 8.9 Feb 23, 2022 · release notes

    OpenSSH 8.9 adds sntrup761x25519 post-quantumpost-quantumCryptography designed to stay secure against a large quantum computer, which could break today's RSA and elliptic-curve keys. NIST standardized the first algorithms in 2024 as ML-KEM, ML-DSA and SLH-DSA. KEX, agent key restrictions, and ssh-keygen match-principals

    • sntrup761x25519-sha512@openssh.com hybrid ECDH/x25519 + Streamlined NTRU Prime post-quantum KEX added to the default KEXAlgorithms list
    • System for restricting forwarding and use of keys added to ssh-agent(1) (agent-restricted keys)
    • ssh-keygen -Y match-principals operation added to perform matching of principals names against an allowed signers file
    • PubkeyAuthentication configuration directive extended to accept unbound and host-bound options

    4 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Built-in support for MD5-hashed passwords is removed from sshd(8) on portable OpenSSH
    • !FIDO security key middleware interface modified, incrementing SSH_SK_VERSION_MAJOR
22. 8.8 Sep 26, 2021 · release notes

    OpenSSH 8.8 adds none argument to CanonicalizePermittedCNAMEs and disables RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it./SHA-1SHA-1A cryptographic hash function standardized by NIST that produces a 160-bit digest; tools use it for file integrity checks, though it is now considered cryptographically broken and unsuitable for collision-resistant applications. by default

    └──▷ USE IT
    Re-enable RSA/SHA-1 authentication for a legacy host that does not support newer algorithms.
    config copy

    Host old-host
      HostkeyAlgorithms +ssh-rsa
      PubkeyAcceptedAlgorithms +ssh-rsa

    • ssh_config(5) CanonicalizePermittedCNAMEs directive now accepts none to disable canonicalization of permitted CNAMEs (previously implicit or unspecified).
    • RSA signatures using the SHA-1 hash algorithm are disabled by default, requiring explicit re-enablement via HostkeyAlgorithms +ssh-rsa and PubkeyAcceptedAlgorithms +ssh-rsa for legacy hosts.

    2 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !RSA signatures using SHA-1 are disabled by default; connections to older SSH implementations may fail unless HostkeyAlgorithms and PubkeyAcceptedAlgorithms are updated in ~/.ssh/config to include +ssh-rsa.
23. 8.7 Aug 20, 2021 · release notes

    OpenSSH 8.7 adds experimental SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel.-backed scp, new ssh_config directives, and key validity intervals in allowed_signers files

    └──▷ USE IT
    Force SFTP-based transfer for scp to avoid SCPSCPSecure Copy Protocol, a file-transfer method built on SSH that encrypts data in transit; cyber tools use it to move files to or from remote hosts without exposing credentials or content./RCP limitations
    shell copy

    scp -s /local/path user@host:/remote/path

    Use SFTP even if the remote doesn't support it (falling back to original protocol via -O if needed, though -s forces SFTP)
    shell copy

    scp -O user@host:/remote/path /local/path

    • Adds scp -s flag to enable experimental SFTP protocol for transfers instead of SCP/RCP
    • Adds -O flag to scp(1) to force use of the original SCP/RCP protocol when SFTP is unavailable or incompatible
    • Adds ForkAfterAuthentication directive to ssh_config(5) as a counterpart to the ssh -f flag
    • Adds StdinNull directive to ssh_config(5) allowing config file control equivalent to the ssh -n CLI flag
    • Adds SessionType directive to ssh_config for configuration-level control equivalent to -N and -s flags

    +2 more show less

    • Allows listing key validity intervals in allowed_signers files used by ssh-keygen(1) signatures
    • Adds -Oprint-pubkey flag to ssh-keygen(8) to print the full public key in a sshsig signature

    7 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !scp(1) remote-to-remote copies now transfer through the local host by default; use -R to select old behavior
    • !Stricter configuration file parser in ssh(1) and sshd(8) rejects options lacking arguments, unterminated quotes, and multiple '=' characters after option name
24. 8.6 Apr 19, 2021 · release notes

    OpenSSH 8.6 adds sftp limits extension and sshd ModuliFile config key

    • Adds limits@openssh.com protocol extension to sftp-server(8) for discovering server limits like maximum packet size and read/write length
    • Updates sftp(1) client to use the limits@openssh.com extension when available to select better transfer lengths
    • Adds ModuliFile keyword to sshd_config to specify the location of the moduli file for DH-GEX

    3 details in Everything

25. 8.5 Mar 3, 2021 · release notes

    OpenSSH 8.5 adds KnownHostsCommand, PerSourceMaxStartups, PermitRemoteOpen and enables UpdateHostKeys

    └──▷ USE IT
    Fetch known hosts from a centralized directory service instead of the local file.
    shell copy

    ssh -o KnownHostsCommand='/usr/local/bin/fetch-hostkeys %h'

    Limit new connection attempts from any single source IP to 10 per minute in sshd.
    config copy

    PerSourceMaxStartups 10
    PerSourceNetBlockSize 8

    Prevent remote forwarding to any destination other than localhost:631 (CUPS printer).
    shell copy

    ssh -o PermitRemoteOpen 'localhost:631' user@host

    • Adds ssh_config KnownHostsCommand option to retrieve known_hosts data via an external command
    • Adds sshd_config PerSourceMaxStartups and PerSourceNetBlockSize directives for per-IP rate limiting of new connections
    • Adds ssh_config PermitRemoteOpen option to restrict destinations when using RemoteForward with SOCKSSOCKSA proxy protocol that relays TCP (and optionally UDP) connections through an intermediary server, letting cyber tools route traffic through a pivot host or anonymizing layer without needing raw network access.

    3 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The first-preference signature algorithm for ssh(1) and sshd(8) changes from ECDSAECDSAThe elliptic-curve signature algorithm behind most TLS certificates, blockchains and many hardware keys. It is one of the algorithms post-quantum signatures are meant to replace. to ED25519
    • !Pre-standardization cipher rijndael-cbc@lysator.liu.se is removed from ssh(1) and sshd(8)
    • !CheckHostIP defaults to disabled in ssh_config
26. 8.4 Sep 27, 2020 · release notes

    OpenSSH 8.4 adds FIDO PIN support, WebAuthnWebAuthnA web standard that lets a browser prove possession of a passkey or hardware key to a website. It is the browser-facing part of FIDO2 sign-in. signature verification, $SSH_ASKPASS_REQUIRE env var, and %k token.

    └──▷ USE IT
    Generate a FIDO2FIDO2The open standard behind passkeys and hardware security keys, where a website checks a signature from the user's device instead of a password. Because the key is bound to the site, phishing pages cannot use it. key that strictly requires the user to enter their PIN on the hardware token before every cryptographic operation.
    shell copy

    ssh-keygen -t ecdsa-sk -O verify-required

    Expand the HostKey variable %k in UserKnownHostsFile to store host keys in individual files per target.
    config copy

    # In ssh_config
    UserKnownHostsFile ~/.ssh/known_hosts.d/%k

    Force enable ssh-askpass even if the environment suggests a terminal is available, useful for scripted GUIGUIA graphical user interface, controls such as windows, buttons and menus. It lets people use software visually rather than entering commands. prompts.
    shell copy

    export SSH_ASKPASS_REQUIRE=yes
    ssh user@host

    • ssh-keygen(1) accepts a new verify-required option to generate FIDO keys that demand a PIN for every use.
    • authorized_keys in sshd(8) gains the verify-required keyword to require user verification (PIN) on FIDO signatures.
    • ssh(1), sshd(8), and ssh-keygen(1) add support for verifying FIDO WebAuthn signatures from web browsers.
    • ssh(1) allows ${ENV} shell-style expansion in CertificateFile, ControlPath, IdentityAgent, IdentityFile, and LocalForward/RemoteForward (for Unix sockets).
    • New $SSH_ASKPASS_REQUIRE environment variable gives control over ssh-askpass usage (enabling/disabling forcibly).

    +4 more show less

    • AddKeysToAgent in ssh_config(5) now accepts a time limit to automatically expire keys in the agent.
    • scp(1) and sftp(1) gain an explicit -A flag to enable agent forwarding, overriding defaults.
    • New %k token in ssh(1) expands to the effective HostKey of the destination.
    • UserKnownHostsFile in ssh_config(5) now supports %-TOKEN, environment variable, and tilde expansion.

    9 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !OpenSSH 8.4 will disable the ssh-rsa public key signature algorithm by default in a near-future release (not yet active in 8.4).
    • !The format of attestation information recorded by ssh-keygen(1) for FIDO keys has changed to include authenticator data.
    • !The API between OpenSSH and FIDO token middleware requires version 7 (SSH_SK_VERSION_MAJOR).
27. 8.3 May 27, 2020 · release notes

    OpenSSH 8.3 adds tri-state IgnoreRhosts, %TOKEN in forwarding, binary KRL dump, and chacha20 preference.

    └──▷ TRY IT
    Configure a local forward using the SSH command's internal token to dynamically resolve the bind address at runtime.
    copy

    $ ssh -L %h:22:user@remote_host:/var/run/ssh.sock user@localhost

    Inspect the contents of a compiled binary key revocation list file.
    copy

    $ ssh-keygen -lQf /etc/ssh/user_krl

    • IgnoreRhosts becomes a tri-state option in sshd_config, accepting the new value shosts-only to allow .shosts but reject .rhosts
    • ssh(1) adds %TOKEN percent expansion support within LocalForward and RemoteForward directives for Unix domain socket forwarding
    • ssh-keygen gains -lQf <path> flags to dump the contents of a binary key revocation list (KRL)
    • sshd_config now allows the IgnoreRhosts directive in any position, including within or after Match blocks
    • OpenSSH prefers the chacha20 implementation from libcrypto over its portable C fallback where available for improved performance

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !sftp(1) now rejects the argument -1 instead of silently ignoring it, matching the behavior of ssh(1) and scp(1)
28. 8.2 Feb 14, 2020 · release notes

    OpenSSH 8.2 adds FIDO/U2F hardware authenticator support with ecdsa-sk and ed25519-sk key types.

    └──▷ USE IT
    Generate a private key backed by a FIDO/U2F security key.
    shell copy

    ssh-keygen -t ecdsa-sk -f ~/.ssh/id_ecdsa_sk

    Connect to a host while excluding the deprecated ssh-rsa algorithm to check for support of stronger algorithms.
    shell copy

    ssh -oHostKeyAlgorithms=-ssh-rsa user@host

    • Adds ecdsa-sk and ed25519-sk public key types for FIDO/U2F hardware authenticators
    • Adds SecurityKeyProvider directive to sshd_config and client config
    • Introduces new ssh-sk-helper(8) binary for FIDO middleware isolation

    3 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Removes diffie-hellman-group14-sha1 from the default key exchange proposal for both client and server
    • !Folds command-line options related to safe prime generation for diffie-hellman-group-exchange-* under the -O flag in ssh-keygen(1)
29. 8.1 Oct 9, 2019 · release notes

    OpenSSH 8.1 adds PKCS#8 key storage, SSH agent signatures, proxy hostname expansion, and host algorithm prepending

    • ssh(1) now allows %n (hostname) to be expanded in ProxyCommand strings, enabling dynamic proxy routing based on the target host.

    1 detail in Everything

    └──▷ BREAKING ON UPGRADE

    • !ssh-keygen(1) changes the default algorithm for signing certificates with an RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it. key from ssh-rsa to rsa-sha2-512; certificates signed by OpenSSH 8.1 will be incompatible with versions prior to 7.2 unless overridden via ssh-keygen -t ssh-rsa.
30. 8.0 Apr 17, 2019 · release notes

    OpenSSH 8.0 adds experimental quantum-resistantquantum-resistantCryptography designed to stay secure against a large quantum computer, which could break today's RSA and elliptic-curve keys. NIST standardized the first algorithms in 2024 as ML-KEM, ML-DSA and SLH-DSA. KEX, PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. ECDSAECDSAThe elliptic-curve signature algorithm behind most TLS certificates, blockchains and many hardware keys. It is one of the algorithms post-quantum signatures are meant to replace., and scp filename checks

    └──▷ USE IT
    Scan an agent's keys to ensure they are usable without removing them.
    shell copy

    ssh-add -T /path/to/key

    Disable scp's strict filename verification to work around wildcard expansion mismatches with legacy servers.
    shell copy

    scp -T user@remote:/path/file ./local_dir/

    • Add support for ECDSA keys in PKCS#11 tokens via ssh, ssh-agent, and ssh-add.
    • Add -T option to scp(1) to disable client-side filename verification checks.
    • Add experimental quantum-computing resistant key exchange method based on Streamlined NTRU Prime 4591^761 and X25519X25519The elliptic-curve key exchange most modern TLS, SSH and WireGuard connections use to agree on a session key. Post-quantum hybrids pair it with ML-KEM..
    • Increase the default RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it. key size to 3072 bits in ssh-keygen(1).
    • Allow -J option as an alias to ProxyJump on scp(1) and sftp(1) command-lines.

    +4 more show less

    • Add -T option to ssh-add(1) to test whether keys in an agent are usable by performing a signature and verification.
    • Add -h flag to chown, chgrp, and chmod commands in sftp(1) to request they do not follow symlinks.
    • Expose $SSH_CONNECTION in the PAMPAMBrokering administrator sessions through a gateway instead of handing out standing credentials. Access is granted for one session, to one target, and recorded. environment within sshd(8).
    • Add a Match final predicate to ssh_config for matching without hostname canonicalisation.

    9 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Remove support for obsolete slash-separated host/port syntax in ListenAddress and PermitOpen in sshd(8).
31. 7.9 Oct 19, 2018 · release notes

    OpenSSH 7.9 adds CA signature algorithm control via CASignatureAlgorithms and KRL SHA256SHA256A cryptographic hash function that turns data into a fixed 256-bit fingerprint. It is used to check integrity; hashing does not encrypt the original data. hash support

    • Adds CASignatureAlgorithms option to sshd_config and ssh_config for controlling allowed CA certificate signature formats.
    • Adds IdentityAgent configuration directive support for environment variable names in ssh_config to allow dynamic agent socket selection.
    • Adds ssh -Q sig query to list supported signature algorithms and ssh -Q help for the full set of supported queries.
    • Enables KeyRevocationList entries in authorized_keys to revoke keys by their SHA256 hash, allowing revocation based on log fingerprints.
    • Adds support for service names from getservbyname(3) in port specifications for both client and server.

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The sshd(8) authentication success/failure log message format changed to include the certificate fingerprint instead of only key ID and CA key fingerprint.
32. 7.8 Aug 24, 2018 · release notes

    OpenSSH 7.8 adds PermitListen, SetEnv, and timing attack countermeasures

    └──▷ USE IT
    Restrict remote port forwarding to specific addresses/ports using the new PermitListen directive
    text copy

    PermitListen localhost,192.168.1.1:8080

    Set specific environment variables on the remote session using the new SetEnv directive in sshd_config
    env copy

    SetEnv MY_VAR=VALUE ANOTHER_VAR=data

    • sshd(8) extends PermitUserEnvironment to accept a whitelist of environment variable names
    • sshd(8) adds the PermitListen directive in sshd_config(5) for controlling remote forwarding addresses/ports
    • sshd(8) adds timing countermeasures (global 5ms + per-user 0-4ms delay) against account enumeration
    • sshd(8) adds the SetEnv directive to explicitly specify environment variables in sshd_config
    • ssh(1) / sshd(8) add support for signature algorithms rsa-sha2-256-cert-v01@openssh.com and rsa-sha2-512-cert-v01@openssh.com

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !ssh-keygen(1) now writes OpenSSH format private keys by default; add -m PEM to generate legacy OpenSSL PEM format keys
    • !sshd(8) removes internal support for S/Key multiple factor authentication; use PAMPAMBrokering administrator sessions through a gateway instead of handing out standing credentials. Access is granted for one session, to one target, and recorded. or BSD auth instead
    • !ssh(1) returns a fatal error if executed as setuid binary or with uid != effective uid; this vestigial support has been removed
    • !sshd(8) PubkeyAcceptedKeyTypes and HostbasedAcceptedKeyTypes now specify signature algorithms rather than key types; omitting new algorithm names may cause authentication failures
    • !sshd(8) changes precedence of session environment variables; ~/.ssh/environment and environment="..." in authorized_keys can no longer override SSH_* variables set implicitly by sshd
33. 7.7 Apr 2, 2018 · release notes

    OpenSSH 7.7 adds XMSS key support, URI protocols, rdomain routing, and expiring keys

    └──▷ USE IT
    Connect to a host using the new URI syntax supported by ssh, scp, and sftp.
    shell copy

    ssh ssh://admin@192.168.1.10

    Bind an outgoing SSH connection to a specific network interface's address.
    shell copy

    ssh -o BindInterface=eth0 user@host

    • Adds URI support to ssh(1), scp(1), and sftp(1) clients, enabling connection strings like ssh://user@host or sftp://user@host/path.

    1 detail in Everything

34. 7.6 Oct 3, 2017 · release notes

    OpenSSH 7.6 adds RemoteCommand, reverse dynamic forwarding, ExposeAuthInfo, and new StrictHostKeyChecking values.

    └──▷ USE IT
    Execute a specific command on remote hosts defined in ~/.ssh/config without typing it every time.
    config copy

    Host myserver
        HostName example.com
        User admin
        RemoteCommand /usr/local/bin/start-monitoring

    Automatically trust new host keys while rejecting changed or invalid ones, safer than accepting all.
    shell copy

    ssh -o StrictHostKeyChecking=accept-new user@example.com

    • Adds RemoteCommand option to ssh(1) config to specify a remote command without using the CLI.
    • Adds reverse dynamic forwarding (-R) support, allowing ssh to act as a SOCKS4/5SOCKS4/5A proxy protocol that relays TCP connections (and UDP in version 5) through an intermediary host, letting cyber tools tunnel traffic through firewalls or pivot points without needing IP-level routing. proxy for the remote host.
    • Adds ExposeAuthInfo option to sshd(8) to expose authentication details via $SSH_USER_AUTH in the session.
    • Expands StrictHostKeyChecking with new values accept-new and off in ssh(1).
    • Adds -q flag to ssh-add(1) for quiet success output.

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !ssh(1) no longer supports SSH protocol version 1, its configuration options, or documentation.
    • !ssh(1) and sshd(8) remove support for the hmac-ripemd160 MAC algorithm.
    • !ssh(1) and sshd(8) remove support for arcfour, blowfish, and CAST ciphers.
    • !ssh(1) refuses RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it. keys shorter than 1024 bits by default.
    • !ssh(1) no longer offers CBC ciphers by default in the configuration.
35. 7.5 Mar 20, 2017 · release notes

    OpenSSH 7.5 adds =- syntax to remove algorithms and deprecates UsePrivilegeSeparation

    └──▷ USE IT
    Disable all CBC ciphers for both client and server configurations using the new =- syntax
    config copy

    Ciphers=+aes256-ctr,aes192-ctr,aes128-ctr,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com -=*cbc

    Update sshd_config to explicitly enable privilege separation as the deprecated option is now ignored or enforced
    config copy

    # Remove or comment out this line, as it is now mandatory by default:
    # UsePrivilegeSeparation yes

    • Adds =- syntax to configuration files (e.g., Ciphers=-*cbc) to easily remove methods from algorithm lists
    • Deprecates the UsePrivilegeSeparation option in sshd_config, making privilege separation mandatory
    • Changes log message format in packet code to include user authentication state (affects log monitoring tools)

    3 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The UsePrivilegeSeparation option is deprecated and privilege separation is now mandatory; setting it to no will no longer work
    • !Log messages emitted by the packet code now include additional information about the user and their authentication state, which may break existing log parsers
36. 7.4 Dec 19, 2016 · release notes

    OpenSSH 7.4 adds proxy multiplexing mode via ssh -O proxy, PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. whitelist in ssh-agent, and new DisableForwarding option.

    └──▷ USE IT
    Globally disable all forwarding types for a specific user in the SSH daemon configuration.
    config copy

    sshd_config snippet: User foo\n  DisableForwarding yes

    Whitelist trusted paths for PKCS#11 modules in the SSH agent.
    shell copy

    ssh-agent -a /tmp/agent.sock -P /usr/lib,/usr/local/lib

    • Adds proxy multiplexing mode to ssh(1) invoked with the -O proxy subcommand, allowing multiplexing clients to communicate with the master process over a Unix-domain socket without file-descriptor passing.
    • Enables ssh-agent to refuse loading PKCS#11 modules from paths outside a trusted whitelist by default, with the path whitelist configurable at run-time.
    • Adds DisableForwarding option to sshd_config that disables X11, agent, TCPTCPA network protocol that delivers a reliable, ordered stream of bytes between two endpoints. It detects lost data and retransmits it., tunnel and Unix domain socket forwarding.
    • Adds curve25519-sha256 key exchange method support in both ssh(1) and sshd(8).
    • Allows ClientAliveInterval and ClientAliveCountMax directives inside Match blocks in sshd_config.

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Removes server support for the SSH v.1 protocol.
    • !Removes 3des-cbc from the client's default cipher proposal in ssh(1).
    • !Removes pre-authentication compression support in sshd(8).
    • !Removes the UseLogin configuration directive and support for having /bin/login manage login sessions in sshd(8).
37. 7.3 Aug 1, 2016 · release notes

    OpenSSH 7.3 adds ProxyJump (-J), IdentityAgent, SHA2 signatures in certs, and ssh_config Include

    └──▷ TRY IT
    Connect to a host via a bastion without manual port forwarding
    copy

    $ ssh -J bastion.example.com target.example.com

    Use a specific gpg-agent socket for authentication
    copy

    $ ssh -o IdentityAgent=/run/user/1000/gnupg/S.gpg-agent.ssh target.example.com

    Load additional configuration files dynamically
    config copy

    Include /etc/ssh/ssh_config.d/*.conf
    Host *.internal
        User admin

    • Add a ProxyJump option and corresponding -J command-line flag to allow simplified indirection through one or more SSH bastions or jump hosts
    • Add an IdentityAgent option to allow specifying specific agent sockets instead of accepting one from the environment
    • Add an Include directive for ssh_config(5) files
    • Support SHA256SHA256A cryptographic hash function that turns data into a fixed 256-bit fingerprint. It is used to check integrity; hashing does not encrypt the original data. and SHA512 RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it. signatures in certificates

    4 details in Everything

38. 7.2 Feb 29, 2016 · release notes

    OpenSSH 7.2 adds AddKeysToAgent, ssh-keygen -c, sha2 RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it. signatures, and restricted keys

    └──▷ USE IT
    Automatically cache a key in the agent upon successful authentication without manual intervention.
    shell copy

    ssh -o AddKeysToAgent=yes user@host

    Fetch the certificate associated with a host key using ssh-keyscan.
    shell copy

    ssh-keyscan -c example.com

    • Adds AddKeysToAgent option to ssh_config to automatically cache private keys in ssh-agent. Available values: yes, no, ask, confirm. Defaults to no.
    • Adds restrict keyword to authorized_keys to apply all current and future key restrictions (e.g., no-pty, no-port-forwarding) at once.
    • Adds -c flag to ssh-keyscan to fetch certificates instead of plain keys.
    • Adds ability to fingerprint multiple public keys from a file using ssh-keygen -lf ~/.ssh/authorized_keys.

    4 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Disables legacy ciphers (blowfish-cbc, cast128-cbc, arcfour variants, rijndael-cbc) and MD5-based HMACs by default in ssh. Users must explicitly re-enable them if needed.
    • !Requires minimum 2048-bit modulus for diffie-hellman-group-exchange; connections attempting to use smaller moduli will fail.
39. 7.1 Aug 21, 2015 · release notes

    OpenSSH 7.1 adds compatibility workarounds for PuTTY and WinSCP, though this is primarily a bugfix release.

    • Adds compatibility workarounds for PuTTY (FuTTY) in ssh(1) and sshd(8).
    • Refines compatibility workarounds for WinSCP in ssh(1) and sshd(8).

    2 details in Everything

40. 7.0 Aug 11, 2015 · release notes

    OpenSSH 7.0 introduces algorithm selection options and append-mode configuration syntax

    • Adds PubkeyAcceptedKeyTypes option to ssh_config(5) to control which public key types are available for user authentication
    • Adds HostKeyAlgorithms option to sshd_config(5) to control which public key types are offered for host authentications
    • Allows appending to default algorithm sets by prefixing values with '+' in Ciphers, MACs, KexAlgorithms, etc.
    • PermitRootLogin now accepts prohibit-password as an unambiguous synonym for without-password

    4 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Support for the legacy SSH version 1 protocol is disabled by default at compile time
    • !The default for the sshd_config(5) PermitRootLogin option has changed from yes to prohibit-password
    • !PermitRootLogin=without-password/prohibit-password now bans all interactive authentication methods, allowing only public-key, hostbased and GSSAPI authentication
41. 6.9 Jul 1, 2015 · release notes

    OpenSSH 6.9 adds AuthorizedPrincipalsCommand, relaxes GSSAPI checks, and promotes ChaCha20 as default cipher

    └──▷ USE IT
    Retrieve authorized principals from a custom script instead of a static file using AuthorizedPrincipalsCommand
    config copy

    AuthorizedPrincipalsCommand /usr/local/bin/get_principals.sh %u %k

    Search for a specific host's key fingerprint in known_hosts without printing the full key block
    copy

    $ ssh-keygen -lF myserver.example.com

    Keep ssh-agent running in the foreground for debugging or integration without verbose output
    copy

    $ ssh-agent -D

    • Adds AuthorizedPrincipalsCommand to sshd_config to retrieve authorized principals from a subprocess.
    • Promotes chacha20-poly1305@openssh.com to be the default cipher for ssh(1) and sshd(8).
    • Adds GSSAPIStrictAcceptorCheck option in sshd_config to relax GSSAPI host credential checks for multihomed hosts.
    • Adds -D flag to ssh-agent to leave it running in the foreground without enabling debug mode.
    • Adds ssh-keygen -lF hostname syntax to search known_hosts and print key hashes rather than full keys.

    5 details in Everything

42. 6.8 Mar 18, 2015 · release notes

    OpenSSH 6.8 adds FingerprintHash, host key rotation via UpdateHostkeys, Match canonical, RevokedHostKeys, and KRL improvements

    └──▷ TRY IT
    Verify a remote host's fingerprint using the new SHA256SHA256A cryptographic hash function that turns data into a fixed 256-bit fingerprint. It is used to check integrity; hashing does not encrypt the original data./SHA2 base64 format
    copy

    $ ssh -o FingerprintHash=sha256 user@host

    Pre-review a complex ssh_config file to debug rules before connecting
    copy

    $ ssh -G host.example.com

    Allow the SSH client to automatically learn and update host keys after authentication
    text copy

    Host *
      UpdateHostkeys yes

    • Adds the FingerprintHash config option to ssh_config(5) and sshd_config(5), changing the default fingerprint algorithm from MD5 to SHA256 and format from hex to base64
    • Adds the UpdateHostkeys config option to ssh_config(5) to enable experimental host key rotation support via a protocol extension
    • Adds the -G flag to the ssh CLI command to parse configuration and dump the result to stdout without connecting
    • Adds the RevokedHostKeys config option to ssh_config(5) to allow text-file or KRL-based revocation of host keys on the client side
    • Adds the Match canonical criteria in ssh_config(5) to allow Match blocks to trigger only in the second config pass

    +1 more show less

    • Adds HostbasedAcceptedKeyTypes and PubkeyAcceptedKeyTypes options to sshd_config(5) to control which public key types will be accepted

    6 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !UseDNS in sshd_config(5) now defaults to no, requiring re-enablement for host-name-based matching
43. 6.7 Oct 6, 2014 · release notes

    OpenSSH 6.7 adds Unix domain socket forwarding, PermitUserRC config, %C escape, and internal library refactoring.

    • unix domain socket forwarding enables remapping remote TCPTCPA network protocol that delivers a reliable, ordered stream of bytes between two endpoints. It detects lost data and retransmits it. ports to local sockets in ssh(1)
    • PermitUserRC sshd_config option controls execution of ~/.ssh/rc in sshd(8)
    • %C escape sequence generates unique paths for LocalCommand and ControlPath in ssh(1)

    3 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Support for tcpwrappers/libwrap has been removed from sshd(8)
    • !CBC ciphers and arcfour* are disabled by default in sshd(8); explicitly configured via Ciphers and MACs options to restore
44. 6.5 Jan 30, 2014 · release notes

    OpenSSH 6.5 adds Ed25519Ed25519A fast elliptic-curve signature scheme with small keys, the default for new SSH keys and common in code signing. It is not quantum-safe. keys, Curve25519Curve25519The elliptic-curve key exchange most modern TLS, SSH and WireGuard connections use to agree on a session key. Post-quantum hybrids pair it with ML-KEM. KEX, sftp protocol extensions, and ssh_config Match/ProxyUseFDPass features

    └──▷ USE IT
    Configure SSH to automatically canonicalize unqualified hostnames before looking up keys
    config copy

    # In ~/.ssh/config
    CanonicalDomains example.com
    CanonicalizeFallbackLocal no

    Use the new Match block to apply specific proxy settings only for a subset of hosts
    config copy

    # In ~/.ssh/config
    Match host *.example.com
        ProxyUseFDPass yes
        ForwardAgent no

    • Adds chacha20-poly1305@openssh.com transport cipher for authenticated encryption
    • Adds Ed25519 public key type support for user and host keys
    • Adds a new private key format using a bcryptbcryptA deliberately slow password-hashing function, so a stolen password database takes far longer to crack by guessing. Argon2 and scrypt are newer alternatives built on the same idea. KDF via the -o flag in ssh-keygen(1)
    • Adds ProxyUseFDPass option to ssh_config(5) to pass file descriptors through ProxyCommands
    • Adds Match keyword to ssh_config(5) for conditional configuration based on hostname, user, or command results

    +3 more show less

    • Adds client-side hostname canonicalisation in ssh(1) using DNS suffixes and rules in ssh_config(5)
    • Adds whitelist/blacklist capability for sftp protocol requests in sftp-server(8)
    • Adds fsync@openssh.com extension to the sftp protocol in sftp-server(8)

    8 details in Everything

45. 6.3 Sep 13, 2013 · release notes

    OpenSSH 6.3 adds ssh-agent support to sshd for encrypted keys and smartcards, new -E log file flag, and sftp resumption.

    └──▷ USE IT
    Configure the server to rekey connections after 1 hour or 1GB of data
    text copy

    RekeyLimit 1H 1G

    Resume a failed file transfer in sftp without re-downloading the existing portion
    copy

    $ sftp -a user@host

    • Adds RekeyLimit option in sshd_config to allow time-based rekeying on the server side
    • Adds -E <logfile> option to ssh(1) and sshd(8) to append debugging logs to a specified file instead of stderr or syslog
    • Adds IgnoreUnknown configuration option to ssh(1) to selectively suppress errors from unknown directives
    • Adds support for submethods in the AuthenticationMethods configuration directive for sshd(8)
    • Adds reget command and -a (append) option to sftp(1) to resume partial downloads

    +1 more show less

    • Enables encrypted hostkeys or hostkeys on smartcards by adding ssh-agent(1) support to sshd(8)

    6 details in Everything

46. 6.2 Mar 22, 2013 · release notes

    OpenSSH 6.2 adds AES-GCMAES-GCMAES encryption in Galois/Counter Mode, which encrypts data and detects tampering in one pass. It is the default cipher for TLS and most disk and cloud encryption. and EtM ciphers, AuthenticationMethods, KRLs, AuthorizedKeysCommand, and more.

    └──▷ USE IT
    Configure sshd to require public key authentication first, then allow password as a fallback.
    text copy

    AuthenticationMethods publickey,password

    Fetch authorized keys from an LDAPLDAPA protocol for querying and modifying directory services, standardized under RFC 4511, commonly used to look up users, groups, and attributes in corporate identity stores like Active Directory. command instead of the filesystem.
    text copy

    AuthorizedKeysCommand /usr/bin/ldap_search %u
    AuthorizedKeysCommandUser nobody

    • Adds aes128-gcm@openssh.com and aes256-gcm@openssh.com ciphers for SSH protocol 2
    • Enables encrypt-then-mac (EtM) MAC modes by default when available
    • Adds support for UMAC-128 MAC as umac-128@openssh.com and umac-128-etm@openssh.com
    • Introduces the AuthenticationMethods sshd_config option to require multiple authentication steps
    • Adds Key Revocation Lists (KRLs) support via ssh-keygen -K and the existing RevokedKeys directive

    +5 more show less

    • Expands AllowTcpForwarding in sshd_config(5) to accept local or remote keywords
    • Adds AuthorizedKeysCommand and AuthorizedKeysCommandUser options to sshd_config(5)
    • Adds -d option to sftp-server(8) to set the starting directory
    • Enables fingerprinting of PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. keys using ssh-keygen -lD pkcs11_provider
    • Makes IdentityOnly apply to keys from PKCS11Provider in ssh_config

    10 details in Everything

47. 6.1 Aug 29, 2012 · release notes

    OpenSSH 6.1 adds ECDSAECDSAThe elliptic-curve signature algorithm behind most TLS certificates, blockchains and many hardware keys. It is one of the algorithms post-quantum signatures are meant to replace. SSHFP support, parallel moduli processing via ssh-keygen options, and enhanced sshd_config Match and banner directives.

    └──▷ TRY IT
    Process the second half of a moduli file in parallel with another worker
    copy

    $ ssh-keygen -G /var/tmp/moduli.out -L 100000 -N 50000

    Append a custom string to the SSH banner while still masking version details (if VersionAddendum allows it, though typically AddBanner does the latter)
    config copy

    # In /etc/ssh/sshd_config
    VersionAddendum MyCustomText

    • Add UsePrivilegeSeparation=sandbox default in sshd_config to enable pre-auth sandboxingsandboxingRunning code inside a restricted environment that limits what it can access or change. The isolation reduces the impact of mistakes or untrusted code, depending on the sandbox's controls. for new installs
    • Add -L (starting line number) and -N (number of lines) options to ssh-keygen(1) for parallel moduli candidate processing
    • Extend Match directive in sshd_config to allow setting AcceptEnv and {Allow,Deny}{Users,Groups} within matched blocks
    • Allow conversion of RSA1 keys to public PEM and PKCS8 formats via ssh-keygen(1)
    • Allow the PermitOpen directive in sshd_config to accept none as an argument to refuse all port-forwarding requests

    +2 more show less

    • Support none as an argument for the AuthorizedPrincipalsFile directive in sshd_config
    • Add VersionAddendum to sshd_config to allow server operators to append arbitrary text to the server SSH protocol banner

    7 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The default value of UsePrivilegeSeparation in sshd_config changes from yes (or privileged) to sandbox for new installs
48. 5.9 Sep 6, 2011 · release notes

    OpenSSH 5.9 adds sandboxingsandboxingRunning code inside a restricted environment that limits what it can access or change. The isolation reduces the impact of mistakes or untrusted code, depending on the sandbox's controls. for privsep child, SHA2 HMACs, ControlPath %L expansion and more

    └──▷ TRY IT
    Force the use of SHA2-512 integrity checking for an SSH session
    copy

    $ ssh -o MACs=hmac-sha2-512 user@host

    Generate all missing host keys with defaults for a fresh system setup
    copy

    $ ssh-keygen -A

    • Introduces mandatory syscall restrictions on the pre-auth UsePrivilegeSeparation=sandbox mode using systrace, seatbelt or rlimit sandboxes
    • Adds new SHA256SHA256A cryptographic hash function that turns data into a fixed 256-bit fingerprint. It is used to check integrity; hashing does not encrypt the original data.-based HMACHMACA keyed hash that proves a message came from someone holding a shared secret and was not altered. Webhooks and API request signing commonly use it. transport integrity modes: hmac-sha2-256, hmac-sha2-256-96, hmac-sha2-512 and hmac-sha2-512-96
    • Adds -A option to ssh-keygen(1) for generating default host keys during system initialization

    3 details in Everything

49. 5.7 Jan 24, 2011 · release notes

    OpenSSH 5.7 adds ECDSAECDSAThe elliptic-curve signature algorithm behind most TLS certificates, blockchains and many hardware keys. It is one of the algorithms post-quantum signatures are meant to replace./ECDH support, scp -3, sftp ln, ssh IPQoS and KexAlgorithms config knobs.

    └──▷ HOW TO FIND IT
    Configure the SSH client to prefer ECDSA key exchange and disable weaker algorithms.
    📍echo KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-nistp384 >> ~/.ssh/config
    Copy a file from server A to server B via your local machine.
    copy

    $ scp -3 user@serverA:/path/to/file user@serverB:/path/to/file

    • KexAlgorithms config knob in ssh(1) / sshd(8) configuration to select key exchange methods and preference order
    • IPQoS option in ssh(1) / sshd(8) configuration to specify arbitrary TOS/DSCP/QoS values
    • scp -3 flag to copy between two remote hosts through the local host
    • sftp client ln command for hard links (use -s or symlink for symlinks)

    4 details in Everything

50. 5.6 Aug 23, 2010 · release notes

    OpenSSH 5.6 adds ControlPersist, cert principals indirection, PEM/PKCS#8 support, and new cert format

    • Adds ControlPersist option to ssh_config(5) to auto-start background multiplex master connections
    • Adds AuthorizedPrincipalsFile option in sshd_config(5) for principal name indirection in certificate authentication
    • Adds principals="name1[,name2,...]" keyword support in ~/.ssh/authorized_keys for per-key permitted principals
    • Extends ssh-keygen(1) with -m option to import (-i) and export (-e) PEM and PKCS#8 keys alongside RFC4716
    • Enables hostbased authentication using certificate host keys via the @cert-authority marker in known_hosts

    +4 more show less

    • Allows ssh-keygen(1) to sign certificates using CA keys stored on a PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. token
    • Introduces new certificate key format ssh-{dss,rsa}-cert-v01@openssh.com with serial numbers and extensions fields
    • Allows ssh_config Hostname options to expand %h for unqualified hostname matching
    • Expands sshd_config(5) Match blocks to accept AuthorizedKeysFile, AuthorizedPrincipalsFile, HostbasedUsesNameFromPacketOnly, and PermitTunnel

    9 details in Everything

51. 5.4 Mar 8, 2010 · release notes

    OpenSSH 5.4 introduces PKCS#11PKCS#11The standard programming interface software uses to ask an HSM, smart card or token to sign or decrypt with a key it holds. Supporting it lets a tool keep its keys in hardware. smartcard support, SSH certificate auth, ssh -W proxy mode, and sftp-server read-only/umask options

    └──▷ TRY IT
    Connect to an intermediate host and forward your local stdout/stdin directly to a specific port on the target server (e.g., for database connections).
    copy

    $ ssh -W localhost:3306 gateway_host

    Configure a trusted Certificate Authority so that sshd accepts keys signed by the CA without manual user approval.
    config copy

    TrustedUserCAKeys /etc/ssh/ca.pub

    Run the sftp-server subsystem in read-only mode to prevent any modifications to files on the remote side.
    copy

    $ sftp-server -R

    • ssh_config / sshd_config: Disable protocol 1 by default (must be explicitly enabled with Protocol 1 to use legacy clients/servers)
    • Adds PKCS#11 token support for smartcards via dlopen(3) on supported platforms, replacing the removed libsectok/OpenSC code
    • New certificate authentication system using OpenSSH's minimal cert format (signed with ssh-keygen(1)) and new config options (TrustedUserCAKeys in sshd_config, or trusted markers in authorized_keys/known_hosts)
    • Adds -W host:port flag to ssh(1) for netcat mode stdio-to-local-port forwarding, enabling use as a ProxyCommand
    • New RevokedKeys option in sshd_config(5) and key revocation markers in known_hosts for sshd/ssh to reject revoked keys

    +3 more show less

    • Adds -R (read-only) mode to sftp-server(8) that disables write operations
    • New command-line option for sftp-server(8) to set an explicit umask
    • sftp(1) client gains human-readable -h flag for ls, tab-completion, recursive get/put, and most scp(1) command-line arguments

    8 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !SSH protocol 1 is disabled by default; clients/servers using it must explicitly enable it with the Protocol 1 directive in ssh_config or sshd_config
52. 5.2 Feb 23, 2009 · release notes

    OpenSSH 5.2 adds dynamic port forward allocation, syslog logging for clients, and ForceCommand argument support

    • Added -y flag to ssh(1) to force logging to syslog instead of stderr for daemonized runs
    • sshd_config(5) ForceCommand directive now accepts command-line arguments for the internal-sftp server
    • ssh(1) ~C escape sequence now supports runtime creation of dynamic (-D) port forwards
    • Added support for SOCKS4ASOCKS4AAn extension of the SOCKS4 proxy protocol that lets the client send a hostname instead of an IP address, delegating DNS resolution to the proxy server rather than the local machine. protocol in ssh(1) dynamic (-D) forwards
    • Enabled remote port forwarding with listen port '0', allowing the server to dynamically allocate and report back a port

    5 details in Everything

53. 5.1 Jul 22, 2008 · release notes

    OpenSSH 5.1 introduces CIDRCIDRA notation for a block of IP addresses, such as 10.0.0.0/24. The number after the slash says how many leading address bits identify the network. matching in sshd_config, multiplexed session limits, VisualHostKey, and sftp df command

    • Adds VisualHostKey to ssh_config(5) to enable experimental SSH fingerprint ASCII visualization for host key verification
    • Adds support for CIDR address/masklen matching in Match address blocks within sshd_config(5)
    • Adds support for CIDR matching in from="..." restrictions within ~/.ssh/authorized_keys
    • Adds -T extended test mode to sshd(8) to print effective configuration and test Match rules with connection parameters
    • Adds MaxSessions option to sshd_config(5) to control the number of multiplexed sessions over a single TCPTCPA network protocol that delivers a reliable, ordered stream of bytes between two endpoints. It detects lost data and retransmits it. connection

    +4 more show less

    • Adds no-more-sessions@openssh.com global request extension in ssh(1) to signal end of session multiplexing
    • Adds -F option to ssh-keygen(1) that searches ~/.ssh/known_hosts for a host by fingerprint when combined with -l
    • Adds AllowAgentForwarding option to sshd_config(5) to control authentication agent forwarding permissions
    • Adds df command to the sftp(1) client to display filesystem space and inode utilization using statvfs@openssh.com

    9 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !ssh-keyscan(1) now defaults to rsa (protocol 2) keys instead of rsa1
54. 4.8 Mar 31, 2008 · release notes

    OpenSSH 4.8 adds chroot support to sshd(8), an internal SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel. server, and BSM auditing.

    └──▷ USE IT
    Isolate users by mounting a directory and forcing SFTP access using the new internal subsystem.
    config copy

    # in /etc/ssh/sshd_config
    Match User sftpuser
        ChrootDirectory /data/sftp
        ForceCommand internal-sftp
        AllowTcpForwarding no

    Prevent banner messages for specific users in a Match block.
    config copy

    # in /etc/ssh/sshd_config
    Match User nopubkey
        Banner none

    • Adds ChrootDirectory option to sshd_config(5) for new user isolation capabilities
    • Enables the internal-sftp subsystem command in sshd_config(5) for simplified chroot configurations
    • Supports Banner=none in sshd_config(5) Match blocks to disable pre-login banners

    3 details in Everything

55. 4.9 Mar 31, 2008 · release notes

    OpenSSH 4.9 adds ChrootDirectory, internal-sftp, no-user authorized_keys option, posix-rename SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel. extension, Banner=none, and more.

    └──▷ USE IT
    Create a restricted SFTP-only chroot environment for deploy users that requires no binary copies inside the jail.
    config copy

    Subsystems {
        Subsystem sftp internal-sftp
    }
    Match User deploy
        ChrootDirectory /data/deploy
        ForceCommand internal-sftp

    • Adds ChrootDirectory directive to sshd_config(5) for jailing sftp subsystems
    • Enables the internal-sftp subcommand in Subsystem or ForceCommand for zero-config chroot SFTP access
    • Supports no-user-rc marker in authorized_keys to disable ~/.ssh/rc execution for a specific key
    • Adds posix-rename@openssh.com extension method to sftp-server(8) for atomic file renaming
    • Adds Banner=none to sshd_config(5) to suppress pre-login banners in specific contexts (e.g. Match blocks)

    +2 more show less

    • Makes ssh(1) ProxyCommands execute using the $SHELL environment variable instead of hardcoded /bin/sh
    • Extends ConnectTimeout option in ssh(1) to cover both TCPTCPA network protocol that delivers a reliable, ordered stream of bytes between two endpoints. It detects lost data and retransmits it. connection and SSH banner exchange phases

    7 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !sftp(1) argument splitting and escaping logic changes, which may alter the interpretation of quoted strings with embedded backslashes
56. 4.7 Sep 5, 2007 · release notes

    OpenSSH 4.7 adds -K flag for GSSAPI auth, UMAC-64 MAC algorithm, and aggressive window updates.

    └──▷ USE IT
    Enable GSSAPI authentication immediately without configuring ssh_config
    shell copy

    ssh -K user@host.example.com

    Force the use of the faster UMAC-64 MAC algorithm for a session
    shell copy

    ssh -o MACs=umac-64@openssh.com user@host.example.com

    • ssh adds -K flag to enable GSSAPI authentication (GSSAPIAuthentication=Yes) in a single invocation
    • New umac-64@openssh.com MAC algorithm added for faster hashing performance (approx. 20% faster than HMACHMACA keyed hash that proves a message came from someone holding a shared secret and was not altered. Webhooks and API request signing commonly use it.-MD5)
    • Enhanced SSH channel window size and more aggressive window update sending improves throughput on high-BDP networks

    3 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !New installations default sshd to SSH Protocol 2 only; existing installations retain previous protocol settings
57. 4.6 Mar 9, 2007 · release notes

    OpenSSH 4.6 adds per-user/host Match directive in sshd_config for granular auth control

    • Adds Match directive to sshd_config allowing enabling and disabling of authentication methods on a per user, group, host and network basis.

    1 detail in Everything

58. 4.4 Sep 27, 2006 · release notes

    OpenSSH 4.4 adds Match conditional configuration and ForceCommand, plus Diffie-Hellman with SHA256SHA256A cryptographic hash function that turns data into a fixed 256-bit fingerprint. It is used to check integrity; hashing does not encrypt the original data..

    └──▷ USE IT
    Restrict specific users to a forced command for automated tasks, ignoring their requested shell or command.
    config copy

    # In /etc/ssh/sshd_config
    Match User deployer
        ForceCommand /usr/local/bin/deploy.sh

    Ensure the SSH connection fails immediately if a port forwarding cannot be established, rather than continuing.
    copy

    $ ssh -o ExitOnForwardFailure=yes -L 8080:localhost:80 user@host

    • Implemented conditional configuration in sshd_config(5) using the Match directive.
    • Added a ForceCommand directive to sshd_config(5).
    • Add support for Diffie-Hellman group exchange key agreement with a final hash of SHA256.
    • Add an ExitOnForwardFailure option to ssh(1).

    4 details in Everything

59. 4.3 Feb 1, 2006 · release notes

    OpenSSH 4.3 adds tun(4) tunneling support for layer 2/3 VPNsVPNsA virtual private network, an encrypted tunnel between devices or networks. It carries traffic across another network as though the endpoints had a private connection.

    • Adds support for tunneling arbitrary network packets over a connection between an OpenSSH client and server via tun(4) virtual network interfaces.
    • Change ssh-keygen to generate a protocol 2 RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it. key when invoked without arguments.

    2 details in Everything

60. 4.2 Sep 1, 2005 · release notes

    OpenSSH 4.2 adds Compression delayed, ControlMaster auto-multiplexing, and long password support

    • Adds Compression delayed as the default server compression method to prevent unauthenticated zlib attacks.
    • Adds ControlMaster=auto and ControlMaster=autoask options for opportunistic connection multiplexing in ssh_config.
    • Adds %h, %p, and %r expansion sequences to ControlPath configuration.
    • Adds support for long passwords (> 8 characters) on UnixWare 7.

    4 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Older OpenSSH clients (<3.5) will refuse to connect to servers using the new default compression unless Compression yes is set in sshd_config or client compression is disabled.
61. 4.1 May 26, 2005 · release notes

    OpenSSH 4.1 adds port forwarding bind address control, hashed known_hosts, multiplexing command mode, and BSM audit.

    • Adds -b <address> to ssh (local/remote/dynamic) and LocalForward/RemoteForward in ssh_config(5) to specify the bind address for port forwarding connections
    • Adds HashKnownHosts configuration directive to ssh(1) and adds search/delete/convert commands to ssh-keygen(1) for managing hashed host names in known_hosts files
    • Adds command mode to ssh(1) connection multiplexing, enabling control of a running master connection (check status, PID, exit)
    • Adds AddressFamily option to sshd(8) for global IPv4/IPv6IPv6The current version of the Internet Protocol, standardized by the IETF, using 128-bit addresses to replace the exhausted IPv4 space. Cyber tools target it because modern networks run dual-stack or IPv6-only. control
    • Adds *EXPERIMENTAL* BSM audit support for Solaris systems in portable OpenSSH

    5 details in Everything

62. 4.0 Mar 9, 2005 · release notes

    OpenSSH 4.0 adds client-side bind address control for port forwarding, hashed known_hosts, and new ssh-keygen management commands.

    └──▷ USE IT
    Configure the SSH client to automatically hash all host keys added to the known_hosts file to prevent neighbor discovery.
    config copy

    # In ~/.ssh/config
    Host *
        HashKnownHosts yes

    • Adds the BindAddress parameter to -L, -R and -D port forwarding directives in ssh(1) and Host blocks in ssh_config(5), allowing local specification of which interface IP a forwarded connection binds to.
    • Adds the HashKnownHosts configuration directive to ssh_config(5) and ssh(1) settings to automatically hash hostnames in ~/.ssh/known_hosts, enhancing user privacy.

    2 details in Everything

63. 3.9 Aug 18, 2004 · release notes

    OpenSSH 3.9 adds IdentitiesOnly, session multiplexing (ControlMaster), environment variable forwarding, port forwarding cancellation, and MaxAuthTries.

    • Adds the IdentitiesOnly option to ssh_config(5) to restrict ssh(1) to keys listed in the config file, ignoring ssh-agent(1)
    • Implements session multiplexing with new ControlMaster and ControlPath options in ssh_config(5) allowing a single connection to carry multiple sessions
    • Adds ability to cancel active remote port forwarding sessions via the ~C escape character in ssh(1)
    • Adds the MaxAuthTries option to sshd_config(5) for controlling authentication attempts per connection
    • Implements environment variable forwarding using SendEnv in ssh_config(5) and AcceptEnv in sshd_config(5)

    +1 more show less

    • Enforces strict permission and ownership checks on ~/.ssh/config, causing ssh(1) to exit if permissions are insecure

    6 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !ssh(1) now exits when ~/.ssh/config has insecure permissions or ownership, instead of attempting to process it
64. 3.1 Apr 9, 2004 · release notes

    OpenSSH 3.1 adds sshd -o support, new sftp buffer options, configurable keygen defaults, and safer X11 forwarding.

    • sshd -o flag added to override configuration options from the command line
    • ssh-keygen no longer defaults to rsa1; users must explicitly specify -t rsa, -t dsa, or -t rsa1 for key generation
    • Default directory for keys and configuration files changed to /etc/ssh/
    • sshd X11UseLocalhost option introduced; X11 forwarding now listens on localhost by default, disabling prior insecure behavior unless reverted via this config key
    • sftp -B, -R, and -P options added for buffer size, remote path specification, and port selection

    +1 more show less

    • public key fingerprint logging enabled with LogLevel=VERBOSE in sshd

    6 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !ssh-keygen no longer defaults to rsa1; explicit -t rsa, -t dsa, or -t rsa1 is now required for key generation
    • !Default directory for keys and configuration files changed from the previous default to /etc/ssh/
    • !sshd X11 forwarding now listens on localhost by default; older X11 clients may fail unless X11UseLocalhost no is set in sshd_config
65. 3.7.1 Feb 25, 2004 · release notes

    OpenSSH 3.7.1 adds SOCKS5SOCKS5A proxy protocol that relays TCP and UDP traffic through an intermediary server without inspecting it, letting cyber tools tunnel connections through firewalls or pivot hosts with minimal overhead. dynamic forwarding, UsePAM runtime toggle, AddressFamily client option, and CTR cipher support

    └──▷ USE IT
    Enable SOCKS5 proxying over an SSH dynamic port forward
    shell copy

    ssh -D 1080 <target>

    Restrict client to IPv4 only connections
    shell copy

    ssh -4 <target>

    • SOCKS5 support has been added to the dynamic forwarding mode in ssh(1)
    • Adds UsePAM directive (config key) that enables/disables PAMPAMBrokering administrator sessions through a gateway instead of handing out standing credentials. Access is granted for one session, to one target, and recorded. support at runtime
    • Adds new AddressFamily client option (CLI flag/config key) to select protocol to use (IPv4 or IPv6IPv6The current version of the Internet Protocol, standardized by the IETF, using 128-bit addresses to replace the exhausted IPv4 space. Cyber tools target it because modern networks run dual-stack or IPv6-only.)
    • aes128-ctr, aes192-ctr, and aes256-ctr ciphers are now supported for SSH protocol 2

    4 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Rhosts authentication has been removed in ssh(1) and sshd(8)
66. 3.8 Feb 24, 2004 · release notes

    OpenSSH 3.8 adds ServerAliveInterval, KerberosGetAFSToken, DNS host keys, untrusted X11 cookies and gssapi-with-mic

    └──▷ TRY IT
    Maintain an SSH connection through a noisy network by sending keep-alive packets every 60 seconds
    copy

    $ ssh -o ServerAliveInterval=60 user@host

    Enable AFS token fetching for KerberosKerberosA network authentication protocol that uses tickets issued by a trusted service. Users and services can prove their identities without sending a password to each application. authentication in the SSH daemon config
    text copy

    # Add to /etc/ssh/sshd_config
    KerberosGetAFSToken yes

    • Adds ServerAliveInterval option to ssh(1) to send application layer keep-alive messages to the server
    • Adds new KerberosGetAFSToken option for sshd(8)
    • Adds support for host keys in DNS via the draft-ietf-secsh-dns-xx.txt standard
    • Changes ssh(1) X11-Forwarding to use untrusted cookies by default, controlled by ForwardX11Trusted
    • Replaces experimental gssapi support with gssapi-with-mic to fix MITM attacks

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The experimental gssapi support is replaced by gssapi-with-mic, breaking compatibility between the two versions
67. 3.7 Sep 16, 2003 · release notes

    OpenSSH 3.7 adds SOCKS5SOCKS5A proxy protocol that relays TCP and UDP traffic through an intermediary server without inspecting it, letting cyber tools tunnel connections through firewalls or pivot hosts with minimal overhead. dynamic forwarding, DNS host keys, AES-CTR ciphers, PAMPAMBrokering administrator sessions through a gateway instead of handing out standing credentials. Access is granted for one session, to one target, and recorded. runtime toggle, and IPv4/6 AddressFamily option.

    └──▷ USE IT
    Enable PAM at runtime via sshd_config
    config copy

    UsePAM yes

    Force IPv6IPv6The current version of the Internet Protocol, standardized by the IETF, using 128-bit addresses to replace the exhausted IPv4 space. Cyber tools target it because modern networks run dual-stack or IPv6-only. address family for the SSH client
    shell copy

    ssh -4 <user>@<host>

    • Adds SOCKS5 support to the dynamic forwarding mode in ssh(1)
    • Adds Experimental support for host keys in DNS (draft-ietf-secsh-dns-xx.txt)
    • Adds Experimental support for aes128-ctr, aes192-ctr, and aes256-ctr ciphers for SSH protocol 2
    • Adds AddressFamily option on client to select protocol to use (IPv4 or IPv6)
    • PAM support may now be enabled/disabled at runtime using the UsePAM directive

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Rhosts authentication has been removed in ssh(1) and sshd(8)
    • !KerberosIV and AFS support has been removed
    • !KerberosV support has been removed from SSH protocol 1
68. 3.6 Mar 31, 2003 · release notes

    OpenSSH 3.6 adds key confirmation via ssh-agent -c, SCPSCPSecure Copy Protocol, a file-transfer method built on SSH that encrypts data in transit; cyber tools use it to move files to or from remote hosts without exposing credentials or content. bandwidth limiting/sFTP progress, ProxyCommand none, and EnableSSHKeysign config

    • Adds -c flag to ssh-add(1) to require user confirmation before a private key is used by ssh-agent(1)
    • Adds support for bandwidth limiting in scp(1)
    • Enables displaying a progress meter in the sftp(1) client
    • Adds EnableSSHKeysign option to the global ssh_config(5) file to re-enable ssh-keysign which is now disabled by default
    • Supports setting ProxyCommand to none in ssh_config(5) to disable proxying

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !ssh-keysign(8) is disabled by default; users must add EnableSSHKeysign yes to their global ssh_config(5) to re-enable it
69. 3.5 Oct 15, 2002 · release notes

    OpenSSH 3.5 adds ssh-agent peer auth, HostbasedAuthentication gating for ssh-keysign, and enhanced sftp ls.

    • ssh-keysign(8) uses RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it. blinding to defend against timing attacks on the RSA host key
    • Enhanced sftp(1) client ls support, including globbing and detailed listings

    2 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The default value for LoginGraceTime in sshd_config(5) has been changed from 600 to 120 seconds
    • !PermitUserEnvironment in sshd_config(5) is now disabled by default
70. 3.3 Jun 21, 2002 · release notes

    OpenSSH 3.3 adds ssh-agent socket binding, timeouts/locking, and server-side compression.

    • ssh-agent can now bind to unix-domain sockets specified on the command line
    • ssh-agent supports locking and timeouts for keys
    • the Compression option is now supported in the server configuration

    3 details in Everything

71. 3.2.3 May 23, 2002 · release notes

    OpenSSH 3.2.3 adds UsePrivilegeSeparation config and improves smartcard/DSA import

    └──▷ TRY IT
    Configure TCPTCPA network protocol that delivers a reliable, ordered stream of bytes between two endpoints. It detects lost data and retransmits it. forwarding while already connected to an SSH session
    copy

    $ ~C -L 8080:localhost:80

    • Adds experimental privilege separation via the UsePrivilegeSeparation sshd_config directive
    • Enables interactive TCP forwarding configuration via the ~C escape command during sessions

    2 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !sshd no longer auto-enables KerberosKerberosA network authentication protocol that uses tickets issued by a trusted service. Users and services can prove their identities without sending a password to each application./AFS; manual configuration is now required to use these features
72. 3.2.2 May 16, 2002 · release notes

    OpenSSH 3.2.2 adds UsePrivilegeSeparation, smartcard/older server improvements, and TCPTCPA network protocol that delivers a reliable, ordered stream of bytes between two endpoints. It detects lost data and retransmits it. forwarding config.

    • Adds UsePrivilegeSeparation configuration option to sshd for experimental privilege separation support
    • Improves smartcard support including OpenSC integration
    • Improves support for older SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel. servers
    • Enables configuration of TCP forwarding during interactive sessions via ~C
    • Adds client side support for PASSWD_CHANGEREQ in protocol v2

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !sshd no longer auto-enables KerberosKerberosA network authentication protocol that uses tickets issued by a trusted service. Users and services can prove their identities without sending a password to each application./AFS
73. 3.0 Nov 6, 2001 · release notes

    OpenSSH 3.0 adds smartcard support, dynamic forwarding, new CLI flags (-F, -b), and key file options.

    └──▷ USE IT
    Start an SSH session with a custom config file located outside the default path.
    shell copy

    ssh -F /path/to/custom/config user@host

    Configure sshd to read authorized keys from a variable path based on the username.
    config copy

    AuthorizedKeysFile /etc/ssh_keys/%u

    Use OpenSSH as a SOCKSSOCKSA proxy protocol that relays TCP (and optionally UDP) connections through an intermediary server, letting cyber tools route traffic through a pivot host or anonymizing layer without needing raw network access. proxy server via dynamic port forwarding.
    shell copy

    ssh -D 1080 user@host

    • Adds -F flag to ssh(1) for specifying a custom configuration file path
    • Adds -b bindaddress option to ssh(1) for binding to a specific network interface
    • Adds ClearAllForwardings command in ssh(1) to remove all port forwardings
    • Adds dynamic forwarding capability to use ssh(1) as a SOCKS server
    • Adds smartcard support in the ssh client and agent

    +10 more show less

    • Adds AuthorizedKeysFile option in sshd_config to specify alternative public key locations
    • Adds Protocol option support in ssh_config and sshd_config to change default protocol version
    • Adds ssh-keyscan(1) support for protocol version 2
    • Adds Rekeying support in protocol version 2
    • Adds improved Kerberos support (KerbIV and KerbV) in protocol v1
    • Adds backward compatibility with older commercial SSH versions >= 2.0.10
    • Adds ExtendedAllowUsers user@host syntax support in sshd_config
    • Adds correct exit status transmission for remote execution with protocol version 2
    • Adds ssh-keygen(1) ability to import private RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it./DSA keys from commercial versions
    • Enables hostkey checking for localhost via NoHostAuthenticationForLocalhost

    15 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !SSH protocol v2 is now the default; previous defaults (v1.3, 1.5) require explicit Protocol configuration to maintain compatibility
    • !The CheckMail option in sshd_config is deprecated as sshd no longer checks for new mail
    • !Files /etc/ssh_known_hosts2, ~/.ssh/known_hosts2, and ~/.ssh/authorized_keys2 are obsolete and considered read-only; future releases may stop reading them entirely
74. 2.9 Apr 29, 2001 · release notes

    OpenSSH 2.9 adds SSHv2 defaults, SOCKSSOCKSA proxy protocol that relays TCP (and optionally UDP) connections through an intermediary server, letting cyber tools route traffic through a pivot host or anonymizing layer without needing raw network access. proxy, rekeying, HostKeyAlgorithms, and more

    └──▷ USE IT
    Enable experimental SOCKS4 proxy on port 1080 for a server
    shell copy

    ssh -D 1080 <server>

    Configure server-side keep-alive intervals in sshd_config
    config copy

    ClientAliveInterval 300
    ClientAliveCountMax 2

    • Adds experimental SOCKS4 proxy support to the client via -D flag, e.g. ssh -D 1080 server
    • Introduces HostbasedAuthentication support in SSH protocol v2
    • Adds rekeying capability with interactive trigger ~R
    • Adds ClientAliveInterval and ClientAliveCountMax server options
    • Adds HostKeyAlgorithms client option

    +1 more show less

    • Improves ListenAddress to support host:port syntax

    6 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !SSH protocol v2 is now the default; users of v1 must add Protocol 1 to their ssh_config or sshd_config
75. OpenSSH 2.5.2p2(2001-03-22) Mar 22, 2001 · release notes

    OpenSSH 2.5.2p2 adds permitopen to authorized_keys, PreferredAuthentications, SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel. globbing/v3, and bubble babble fingerprints.

    └──▷ TRY IT
    Restrict local port forwarding to localhost on port 80.
    copy

    $ echo "permitopen localhost:80 ssh-rsa AAAA..." >> ~/.ssh/authorized_keys

    Scan a host and generate bubble babble fingerprints for sharing.
    copy

    $ ssh-keygen -lf ~/.ssh/id_rsa.pub

    • Adds permitopen option to authorized_keys to restrict port forwarding
    • Adds PreferredAuthentications client option to specify authentication method order
    • Enables SFTP client globbing (get *, put *) and adds -b batch file support for automated transfers
    • Adds support for SFTP protocol v3 (draft-ietf-secsh-filexfer-01.txt)
    • Adds bubble babble format output to ssh-keygen -lf for fingerprint exchange with SSH.COM implementations

    5 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !The --with-egd-pool configure option is deprecated in favour of --with-prngd-socket and --with-prngd-port for PRNGd entropy collection.
76. OpenSSH 2.5.1p1(2001-02-19) Feb 19, 2001 · release notes

    OpenSSH 2.5.1p1 adds SSH2 agent forwarding, sftp client, ssh-keyscan, RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it./DSA key support and new config options

    • Adds agent forwarding for SSH 2 protocol sessions
    • Adds -R flag to ssh for remote port forwarding support
    • Adds interactive sftp client working for both SSH protocol versions
    • Adds ssh-keyscan tool to the distribution
    • Enables RSA host and user keys generation via ssh-keygen -t rsa

    +7 more show less

    • Supports DSA keys alongside RSA for SSH 2 protocol authentication
    • Introduces HostKeyAlias option in client configuration
    • Makes ReverseMappingCheck optional in sshd_config
    • Adds sshd -u0 option to disable DNS lookups on connection
    • Expands PermitRootLogin values to include forced-commands-only and no
    • {Allow,Deny}Groups now support supplementary groups
    • Adds ssh -t flag for multiple forced tty allocation

    12 details in Everything

77. OpenSSH 2.3.0p1(2000-11-06) Nov 6, 2000 · release notes

    OpenSSH 2.3.0p1 adds Rijndael (AES) support, SFTPSFTPSSH File Transfer Protocol, a file transfer standard built on top of SSH that provides encrypted upload, download, and remote file management; cyber tools use it to move files or exfiltrate data over an authenticated, encrypted channel. server, Cygwin platform, and S/key auth.

    • Adds Ciphers configuration directive to enable Rijndael (AES) support for SSH2
    • Adds single-des cipher for SSH1 interoperability with Cisco routers via -c des flag or Cipher des config directive
    • Adds S/key authentication support for SSH2 using kbd-interactive auth
    • Adds expired password change capability through PAMPAMBrokering administrator sessions through a gateway instead of handing out standing credentials. Access is granted for one session, to one target, and recorded. integration
    • Adds -o option support to the scp command

    5 details in Everything

78. OpenSSH 2.2.0p1(2000-09-01) Sep 1, 2000 · release notes

    OpenSSH 2.2.0 adds DSA key support, MaxStartups rate limiting, hostname logging, and SSH2 escape char.

    • Adds MaxStartups option to sshd for Random Early Drop connection rate limiting
    • Adds -u flag to sshd to log hostnames instead of IP addresses in wtmp when UseLogin is yes
    • Enables DSA key support in ssh-agent
    • Enables Escape character ~' support in SSH2 protocol

    4 details in Everything

79. OpenSSH 2.1.1p3(2000-07-12) Jul 12, 2000 · release notes

    OpenSSH 2.1.1p3 introduces MaxStartups directive and changes FallBackToRsh default

    • Adds the MaxStartups configuration directive to mitigate connection flooding attacks by limiting unauthenticated connections.
    • Changes the default value of the FallBackToRsh directive to no.

    2 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !FallBackToRsh now defaults to no, requiring edits to /etc/ssh_config or ~/.ssh/config for previous behavior.
80. 2.1.1p2 Jul 1, 2000 · release notes

    OpenSSH 2.1.1p2 adds shadow password expiry, Irix array sessions, and initial Tru64/NeXT platform support.

    • Adds shadow password expiry support (without password change capability)
    • Adds Irix 6.x array session handling including project IDs and system audit trail IDs
    • Adds initial Tru64 / OSF SIA (Security Integration Architecture) support

    3 details in Everything

81. OpenSSH 2.1.0p1(2000-05-09) May 9, 2000 · release notes

    OpenSSH 2.1.0 adds SSH2 protocol support and built-in entropy collection.

    • Incorporates support for the SSH2 protocol, offering standards compliance and operation without patented RSARSAThe oldest widely used public-key algorithm, for both encryption and signatures, with security resting on factoring large numbers. A large quantum computer would break it..
    • Adds built-in entropy collection, removing the requirement for EGD on systems lacking a /dev/random driver.

    2 details in Everything

    └──▷ BREAKING ON UPGRADE

    • !Requires OpenSSL version 0.9.5 or later to compile.