CVE-2026-39831 — Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh
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 w…
Published: 2026-05-22 · CVSS: 9.1 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7