The OpenSSH project, developed and maintained under the OpenBSD umbrella, announced the release of OpenSSH 10.3, a maintenance update now available for download from the project’s official mirrors.
This release includes several potentially incompatible changes. OpenSSH no longer supports legacy implementations that do not allow rekeying; these connections will now fail when rekeying is required. Plus, certificates with empty principals are also no longer treated as wildcards.
Wildcard matching in certificates has also changed. Wildcards are now consistently supported for host certificates, but are no longer accepted for user certificates. Additionally, the SSH client now validates user and host names provided via the command line for ProxyJump (-J) options, reducing shell injection risks from untrusted input.
OpenSSH 10.3 addresses several security issues. One SSH flaw could allow command execution in configurations where user-controlled input is expanded through configuration tokens. Another sshd issue could cause incorrect principal matching when certificates contain comma-separated values under certain conditions in authorized_keys. The release also resolves a long-standing SCP issue where setuid and setgid bits were not cleared when downloading files as root in legacy mode.
Additional fixes improve algorithm handling for ECDSA keys, ensuring only explicitly configured algorithms are accepted. Issues with connection multiplexing confirmation checks have also been corrected. Other minor fixes enhance robustness in configuration directives, PAM integration, and logging.
Regarding new features, OpenSSH now supports IANA-assigned codepoints for SSH agent forwarding, aligning with ongoing standardization. The ssh-agent and ssh-add tools now support querying protocol extensions, including a new -Q option in ssh-add.
Usability improvements include new multiplexing commands in SSH. Users can now query connection details with ssh -O conninfo and inspect active channels using ssh -O channels. Moreover, the new escape sequence (~I) provides similar information during interactive sessions.
On the configuration side, there is added support for multiple files in the RevokedHostKeys and RevokedKeys directives. Plus, the sshd server now includes an “invaliduser” penalty in PerSourcePenalties, enabling administrators to manage failed login attempts for non-existent users. Penalty timing precision has also been enhanced by using floating-point values.
Finally, key handling improvements include support for writing ED25519 keys in PKCS8 format and expanded support for FIDO/WebAuthn signatures, now enabled by default. Performance enhancements have also been made, especially for the sntrup761 key exchange algorithm.
For more information, see the changelog.
