CVE-2026-39831 PUBLISHED

Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh

Assigner: Go
Reserved: 07.04.2026 Published: 22.05.2026 Updated: 22.05.2026

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.

Product Status

Vendor golang.org/x/crypto
Product golang.org/x/crypto/ssh
Versions Default: unaffected
  • affected from 0 to 0.52.0 (excl.)

Credits

  • NCC Group Cryptography Services, sponsored by Teleport

References

Problem Types

  • CWE-290: Authentication Bypass by Spoofing