Yubico YubiKey 5.4.1 through 5.7.3 before 5.7.4 has an incorrect FIDO CTAP PIN/UV Auth Protocol Two implementation. It uses the signature length from CTAP PIN/UV Auth Protocol One, even when CTAP PIN/UV Auth Protocol Two was chosen, resulting in a partial signature verification.
The product uses an authentication mechanism to restrict access to specific users or identities, but the mechanism does not sufficiently prove that the claimed identity is correct.
Attackers may be able to bypass weak authentication faster and/or with less effort than expected.