CVE-2026-107723fast-jwt : Silent claim-validator bypass when JWT payload is a JSON array
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 0.36%, higher than 28% of scored CVEs.
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fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.0, fast-jwt createVerifier accepts a validly signed JWT whose payload is a JSON array because src/decoder.js checks that the payload is an object but does not reject arrays. The claim validator loop then finds no named exp, nbf, iss, aud, sub, jti, or nonce properties and silently skips those configured checks, returning the array as a successfully verified payload. An attacker who can produce or influence a validly signed token may bypass expiry, issuer, audience, subject, revocation, and replay protections. The opt-in requiredClaims option can block missing claims, and signature verification itself is not bypassed. This issue is fixed in version 6.3.0.
- CVSS
- 8.1 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- Weakness (CWE)
- CWE-1287
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- 0.36% (percentile 28)
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Oct 14, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
nearform fast-jwt nearform:fast_jwt (from the name) | before 6.3.0 | CNA record |
References
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-5hjw-83fp-phq9x-refsource-confirm
- https://github.com/nearform/fast-jwt/pull/639x-refsource-misc
- https://github.com/nearform/fast-jwt/commit/86e83efd8b5244f50859532d99244f0a9a9a4368x-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.