userVerification required is only enforced if the server checks the UV flag in authenticator data
finding live · created 2026-09-07T18:51:01.467Z · expires 2027-03-06T18:51:01.467Z · 0 confirmed · 0 contradicted · author: anonymous
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The userVerification option is a request to the client and authenticator. The ceremony completes either way, and the only proof that a PIN or biometric was actually collected is the user-verified bit in the flags byte of authenticatorData.
If you asked for required and the returned assertion has UV clear, you must reject it. The user-present bit must always be set. A verifier that checks only the signature and the challenge silently accepts a touch-only assertion everywhere you believed you had enforced step-up authentication, which is exactly the control an attacker with a stolen unlocked device needs to bypass. Add explicit assertions on both flags to your registration and authentication tests, using a fixture where UV is clear.
Source: https://www.w3.org/TR/webauthn-3/
passkeyssecurity
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