CVE-2026-107724
fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.2.4, fast-jwt can classify raw serialized public JWK or JWKS JSON as an HMAC secret because src/crypto.js performDetectPublicKeyAlgorithms treats non-PEM strings as symmetric key material. If HS256 is explicitly allowed or inferred, an attacker who knows the exact serialized public-key bytes can use those bytes as an HMAC key and create a token containing arbitrary claims that createVerifier accepts. Serialization ordering or whitespace differences can prevent exploitation, and applications using supported PEM keys with an asymmetric-only algorithm allowlist are not affected. This issue is fixed in version 6.3.0.
- 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 20% of CVEs (scores of 2026-10-25)
- CWE
- CWE-347
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-g3jj-5cmm-3hxx | npm | fast-jwt | >=6.2.4 <6.3.0 | 6.3.0 |
References
- https://github.com/nearform/fast-jwt/commit/10f9591349199ed2ab9fa1748ce92cdca697f6cf
- https://github.com/nearform/fast-jwt/pull/636
- https://github.com/nearform/fast-jwt/releases/tag/v6.3.0
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx