CVE-2026-39831

Summary

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 Software

VendorProductVersion RangeStatus
golang.org/x/cryptogolang.org/x/crypto/ssh0 < 0.52.0affected

Weaknesses

  • CWE-290: Authentication Bypass by Spoofing

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: yes
    • Technical Impact: total

References