CVE-2026-39831: Golang Crypto

Critical severity, CVSS 9.1. EPSS: 0.5% chance of exploitation in the next 30 days.

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 products

• Golang Crypto: before 0.52.0 (fixed in 0.52.0)

Published 2026-05-22. Last modified 2026-07-23.