CVE-2026-107722
criticalfast-jwt provides fast JSON Web Token (JWT) implementation.
fast-jwt provides fast JSON Web Token (JWT) implementation. From 6.2.0 until 6.3.0, fast-jwt can misclassify RSA public-key text as an HMAC secret when the key has non-whitespace content before its PEM header. In src/crypto.js, performDetectPublicKeyAlgorithms trims whitespace but publicKeyPemMatcher remains start-anchored, so comments, control characters, zero-width characters, or wrapper text can prevent PEM detection and reach the HMAC fallback. An attacker who knows the public key bytes can sign arbitrary HS256 claims with that public material when HS256 is inferred or allowed, resulting in authentication or authorization bypass. An asymmetric-only algorithm allowlist prevents the attack. This issue is fixed in version 6.3.0.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Affected products
Not reported by the source (unknown — not "none").
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
No vendor advisory or patch reference tagged by NVD. Check the references below.
References
- https://github.com/nearform/fast-jwt/commit/d96bbc6c5336055a6dbfa318fdbab01197264cfa security-advisories@github.com
- https://github.com/nearform/fast-jwt/pull/632 security-advisories@github.com
- https://github.com/nearform/fast-jwt/releases/tag/v6.3.0 security-advisories@github.com
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-ww5h-9m49-7xx4 security-advisories@github.com
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-ww5h-9m49-7xx4 134c704f-9b21-4f2e-91b3-4a467353bcc0