CVE-2026-39831
Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh
9.1
CRITICAL
CVSS 3.1
EPSS 0.03%
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.
How to fix CVE-2026-39831
To remediate CVE-2026-39831, upgrade the affected package to a fixed version below.
- —no fix listed
- —upgrade to 0.52.0 or later
Is CVE-2026-39831 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0
- from 0, < 0.52.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | CRITICAL9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |