Vulnerability · Published Aug 28, 2026 · Assigned by Go
CVE-2026-56854Source-address critical option not enforced for non-public-key auth callbacks in golang.org/x/crypto/ssh
High 7.5
In plain English
A high-severity incorrect authorization in golang.org/x/crypto/ssh from golang.org/x/crypto. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | golang-go.crypto | no fix listed | DEBIAN-CVE-2026-56854 |
| Debian:13 | golang-go.crypto | no fix listed | DEBIAN-CVE-2026-56854 |
| Debian:14 | golang-go.crypto | 1:0.55.0-1 | DEBIAN-CVE-2026-56854 |
| Go | golang.org/x/crypto | 0.55.0 | GO-2026-6303 |
| Ubuntu:26.10 | golang-go.crypto | no fix listed | UBUNTU-CVE-2026-56854 |
| Ubuntu:22.04:LTS | google-guest-agent | no fix listed | UBUNTU-CVE-2026-56854 |
| Ubuntu:24.04:LTS | google-guest-agent | no fix listed | UBUNTU-CVE-2026-56854 |
| Ubuntu:26.04:LTS | google-guest-agent | no fix listed | UBUNTU-CVE-2026-56854 |
| Ubuntu:26.10 | google-guest-agent | no fix listed | UBUNTU-CVE-2026-56854 |
| Ubuntu:22.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-56854 |
| Ubuntu:24.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-56854 |
| Ubuntu:26.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-56854 |
| Ubuntu:26.10 | snapd | no fix listed | UBUNTU-CVE-2026-56854 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| golang.org/x/crypto | golang.org/x/crypto/ssh | 0 – before 0.55.0 |
Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N