CVE-2026-56854: Source-address critical option not enforced for non-public-key auth callbacks in golang.org/x/crypto/ssh

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-28 · updated 2026-09-03
Weakness: CWE-863

Description

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: before 0.55.0 — fixed in 0.55.0
golang.org/x/crypto/ssh: before 0.55.0 — fixed in 0.55.0

How to fix

Upgrade to a fixed version: Golang.Org/X/Crypto 0.55.0; golang.org/x/crypto/ssh 0.55.0. Check the vendor advisory for mitigations.

References

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