Vulnerability · Published May 22, 2026 · Assigned by Go
CVE-2026-39831Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh
Critical 9.1
In plain English
A critical-severity security flaw 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 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
The Verify() method for FIDO/U2F security key types (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a "no-touch-required" extension in Permissions.Extensions from PublicKeyCallback.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | golang-go.crypto | no fix listed | DEBIAN-CVE-2026-39831 |
| Debian:13 | golang-go.crypto | no fix listed | DEBIAN-CVE-2026-39831 |
| Debian:14 | golang-go.crypto | 1:0.52.0-1 | DEBIAN-CVE-2026-39831 |
| Go | golang.org/x/crypto | 0.52.0 | GO-2026-5019 |
| Go | golang.org/x/crypto | 0.52.0 | GHSA-89gr-r52h-f8rx |
| Ubuntu:25.10 | golang-go.crypto | no fix listed | UBUNTU-CVE-2026-39831 |
| Ubuntu:22.04:LTS | google-guest-agent | 20250116.00-0ubuntu1~22.04.3 | UBUNTU-CVE-2026-39831 |
| Ubuntu:24.04:LTS | google-guest-agent | 20250116.00-0ubuntu1~24.04.4 | UBUNTU-CVE-2026-39831 |
| Ubuntu:25.10 | google-guest-agent | 20250506.01-0ubuntu1.2 | UBUNTU-CVE-2026-39831 |
| Ubuntu:26.04:LTS | google-guest-agent | 20250506.01-0ubuntu2.1 | UBUNTU-CVE-2026-39831 |
| Ubuntu:22.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-39831 |
| Ubuntu:24.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-39831 |
| Ubuntu:25.10 | snapd | no fix listed | UBUNTU-CVE-2026-39831 |
| Ubuntu:26.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-39831 |
| Ubuntu:26.10 | snapd | no fix listed | UBUNTU-CVE-2026-39831 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| golang.org/x/crypto | golang.org/x/crypto/ssh | 0 – before 0.52.0 |