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 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 3.1
- 7.4
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - EPSS
- 0.3% chance of exploitation in the next 30 days; higher than 25% of CVEs (scores of 2026-10-25)
- CWEs
- CWE-20, CWE-347
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-8wpc-h4q6-8fxv | npm | fast-jwt | <6.3.1 | 6.3.1 |
References
- https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534
- https://github.com/nearform/fast-jwt/pull/649
- https://github.com/nearform/fast-jwt/releases/tag/v6.3.1
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv