OpenSSH vulnerabilities

Summary

Christos Papakonstantinou discovered that the OpenSSH scp tool incorrectly handled the legacy scp protocol (-O) option. This could result in certain files being installed setuid or setgid, contrary to expectations. (CVE-2026-35385) Florian Kohnhäuser discovered that OpenSSH incorrectly handled shell metacharacters in usernames within a command line. When untrusted usernames and non-default configurations using % in ssh_config are being used, an attacker could possibly use this issue to execute arbitrary code. (CVE-2026-35386) Christos Papakonstantinou discovered that OpenSSH incorrectly handled parsing the PubkeyAcceptedAlgorithms and HostbasedAcceptedAlgorithms options. This could result in unintended ECDSA algorithms being used, contrary to expectations. (CVE-2026-35387) Michalis Vasileiadis discovered that OpenSSH incorrectly handled proxy-mode multiplexing sessions. This could result in no confirmation being asked, contrary to expectations. (CVE-2026-35388) Vladimir Tokarev discovered that OpenSSH incorrectly handled certificates with the principal name containing a comma character when using user-trusted CA keys in authorized_keys and an authorized_keys principals="" option that lists more than one principal. This could result in inappropriate principal matching, contrary to expectations. (CVE-2026-35414) Affected Ubuntu releases: 26.04, 25.10, 24.04, 22.04. CVEs: CVE-2026-35414, CVE-2026-35387, CVE-2026-35386, CVE-2026-35388, CVE-2026-35385.