CVE-2026-39831

CRITICAL

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.

CVSS v3 vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected routers (0)

No routers currently mapped to this CVE in our database.

External references

• NIST NVD
• MITRE CVE