CVE-2026-107720
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 e
CVSS
7.4
High
EPSS
0.3%
p26
KEV
—
Exploit Today
8
0-100
Published: Oct 8, 2026 · Last modified: Oct 9, 2026 · CWE-20 · CWE-347
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.
- github.comhttps://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534
- github.comhttps://github.com/nearform/fast-jwt/pull/649
- github.comhttps://github.com/nearform/fast-jwt/releases/tag/v6.3.1
- github.comhttps://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv
- github.comhttps://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv