CVE-2026-56854: Golang.org/x/crypto Golang.org/x/crypto/ssh

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

The source-address critical option in the Permissions returned by an authentication callback was only enforced for the PublicKeyCallback and VerifiedPublicKeyCallback paths, extending the fix for CVE-2026-46595. Permissions returned by the PasswordCallback, KeyboardInteractiveCallback, NoClientAuthCallback, and GSSAPIWithMICConfig.AllowLogin callbacks were not validated against the client's remote address, so a source-address restriction set by those callbacks was silently ignored. The check is now applied to the Permissions returned by any authentication callback.

Affected products

• Golang.org/x/crypto Golang.org/x/crypto/ssh: before 0.55.0 (fixed in 0.55.0)

Published 2026-08-28. Last modified 2026-09-03.