CVE-2026-107724fast-jwt treats raw public JWK JSON as an HMAC secret, enabling HS256 token forgery
Updated under an hour ago ()
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It affects nearform fast-jwt. Add what you run to find out whether that includes you.
EPSS puts the chance of exploitation in the next 30 days at 0.22%, higher than 12% of scored CVEs.
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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
- 7.4 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weakness (CWE)
- CWE-347
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- 0.22% (percentile 12)
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Oct 9, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
nearform fast-jwt nearform:fast_jwt (from the name) | from 6.2.4, < 6.3.0 | CNA record |
References
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxxx-refsource-confirm
- https://github.com/nearform/fast-jwt/pull/636x-refsource-misc
- https://github.com/nearform/fast-jwt/commit/10f9591349199ed2ab9fa1748ce92cdca697f6cfx-refsource-misc
- https://github.com/nearform/fast-jwt/releases/tag/v6.3.0x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.