CVE-2026-107720

CVE-2026-107720 · fast-jwt: createVerifier accepts unsigned JWTs when key is '' or null and algorithms is explicitly set

This page contains facts from public vulnerability sources. Check the original advisory before updating.

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.1, fast-jwt createVerifier accepts an unsigned JWT when key is an empty string or null and algorithms is a non-empty allowlist. Falsy synchronous keys bypass prepareKeyOrSecret, allowedAlgorithms remains active, hasKey is false, and the empty signature avoids the verifySignature gate. An attacker can therefore submit a token containing arbitrary claims without possessing a signing key, resulting in authentication or authorization bypass. Claim validators still run, and non-empty keys, an empty key without algorithms, and the async key resolver path do not have this behavior. This issue is fixed in version 6.3.1.

CVSS 7.4 · High · EPSS 0.3% · Fix available

Published

2026-10-08T21:44:06.843Z

Updated

2026-10-09T14:32:14.931Z

Stack: node

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