Auth bypass in widely-used libssh for Kerberos-enabled SSH servers; enables account impersonation and lateral movement across enterprise environments.
CVE-2026-59851
libssh GSSAPI key-exchange flaw lets Kerberos users impersonate arbitrary local users.
Is CVE-2026-59851 being exploited?
Not confirmed. CVE-2026-59851 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.29% probability of exploitation in the next 30 days.
How severe is CVE-2026-59851?
CVE-2026-59851 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-59851?
Yes. A fix has been recorded for CVE-2026-59851. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-59851 affect?
CVE-2026-59851 affects libssh, SSH servers using libssh with GSSAPIKeyExchange enabled, Appliances/embedded devices bundling libssh. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-59851?
Disable GSSAPIKeyExchange immediately and apply vendor patch when available
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated Kerberos principals can log in as arbitrary local users (authentication bypass), enabling lateral movement and privilege access.
Immediate action required