CVE-2026-39831

Description

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 breakdown

Affected products

• Golang / crypto0.52.0
• golang.org/x/crypto / golang.org/x/crypto/ssh0 – 0.52.0

References

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