CVE-2026-39831
Published: 22 May 2026
Summary
CVE-2026-39831 is a critical-severity Missing Authorization (CWE-862) vulnerability in Golang Crypto. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Multi-Factor Authentication (T1556.006); ranked at the 29.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-31395
Vulnerability details
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"…
more
extension in Permissions.Extensions from PublicKeyCallback.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Missing user presence verification in FIDO key auth directly bypasses intended MFA/hardware token check.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Requiring an access control policy ensures authorization checks are defined and applied for critical functions.
Reviews of access controls detect missing authorization checks on critical functions or resources.
Documenting permitted unauthenticated actions prevents missing authorization by making all exceptions explicit and subject to organizational review.
Requiring attribute association with information prevents authorization from being performed without necessary security or privacy context.
Mandating authorization prior to allowing remote connections addresses missing authorization for remote access.
Mandating authorization before wireless connections are allowed prevents missing authorization for wireless access.
The control requires authorization before allowing mobile device connections, directly mitigating missing authorization for system access.
Requiring approvals for account creation and specifying authorizations ensures authorization is not missing for system access.