CVE-2026-39831

CRITICAL 9.1

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

CVSS Score

9.1

EPSS Score

0.0%

EPSS Percentile

2th

The Verify() method for FIDO/U2F security key types ([email protected], [email protected]) 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.

Vendor	golang.org/x/crypto
Product	golang.org/x/crypto/ssh
Published	May 22, 2026
Last Updated	May 22, 2026

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Affected Versions

golang.org/x/crypto / golang.org/x/crypto/ssh

0 < 0.52.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

go.dev: https://go.dev/issue/79566 groups.google.com: https://groups.google.com/g/golang-announce/c/a082jnz-LvI go.dev: https://go.dev/cl/781662 pkg.go.dev: https://pkg.go.dev/vuln/GO-2026-5019

Credits

NCC Group Cryptography Services, sponsored by Teleport