CVE-2026-39831: critical vulnerability in golang.org/x/crypto/ssh
Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh
Published
28Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 9.1epss 0.5%
exploitation probability
0.5%top 59% of all CVEs
observed exploitation
nono source reports it
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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Affected products
golang.org/x/crypto · golang.org/x/crypto/sshRelated CVEs — golang.org/x/crypto/ssh
In the same product, most dangerous first.
CVE-2024-45337CRITICALMisuse of connection.serverAuthenticate may cause authorization bypass in golang.org/x/cryptoEPSS 3.2%CVE-2025-22869HIGHPotential denial of service in golang.org/x/cryptoEPSS 0.9%CVE-2026-39830CRITICALInvoking client can cause server deadlock on unexpected responses in golang.org/x/crypto/sshEPSS 0.7%CVE-2026-39834CRITICALInvoking infinite loop on large channel writes in golang.org/x/crypto/sshEPSS 0.6%CVE-2025-58181MEDIUMUnbounded memory consumption in golang.org/x/crypto/sshEPSS 0.6%CVE-2026-46595CRITICALInvoking VerifiedPublicKeyCallback permissions skip enforcement in golang.org/x/crypto/sshEPSS 0.6%