CVE-2026-107722 — fast-jwt provides fast JSON Web Token (JWT) implementation.
Description
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 v3.1 base metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCritical severity
Band computed from the CVSS base score, not the source's own label — so it means the same thing across every feed.
AV
Network
Attack Vector
AC
Low
Attack Complexity
PR
None
Privileges Required
UI
None
User Interaction
S
Unchanged
Scope
C
High
Confidentiality
I
High
Integrity
A
High
Availability
References
- advisory[email protected]https://github.com/nearform/fast-jwt/commit/d96bbc6c5336055a6dbfa318fdbab01197264cfa
- advisory[email protected]https://github.com/nearform/fast-jwt/pull/632
- advisory[email protected]https://github.com/nearform/fast-jwt/releases/tag/v6.3.0
- advisory[email protected]https://github.com/nearform/fast-jwt/security/advisories/GHSA-ww5h-9m49-7xx4
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