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.

PUBLISHED Reserved 2026-04-07 | Published 2026-05-22 | Updated 2026-05-22 | Assigner Go

Problem types

CWE-290: Authentication Bypass by Spoofing

Product status

Credits

NCC Group Cryptography Services, sponsored by Teleport

References

go.dev/issue/79566

groups.google.com/g/golang-announce/c/a082jnz-LvI

go.dev/cl/781662

pkg.go.dev/vuln/GO-2026-5019

cve.org (CVE-2026-39831)

nvd.nist.gov (CVE-2026-39831)

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