{"id":"CVE-2026-107720","published":"2026-10-08T22:17:28.090","lastModified":"2026-10-09T15:17:08.947","description":"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.","cvssScore":7.4,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","cwes":["CWE-20","CWE-347"],"vendors":[],"products":[],"references":[{"url":"https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534","tags":[]},{"url":"https://github.com/nearform/fast-jwt/pull/649","tags":[]},{"url":"https://github.com/nearform/fast-jwt/releases/tag/v6.3.1","tags":[]},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv","tags":[]},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv","tags":[]}],"exploitRefs":[{"url":"https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534","tags":[]},{"url":"https://github.com/nearform/fast-jwt/pull/649","tags":[]},{"url":"https://github.com/nearform/fast-jwt/releases/tag/v6.3.1","tags":[]},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv","tags":[]},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv","tags":[]}],"hasPoc":true,"ai":null}