CVE-2026-107723
An attacker who can produce or influence a validly signed token may bypass expiry, issuer, audience, subject, revocation, and replay protections.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.46%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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 3.1
- 8.1 HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 0.46% probability · 39th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-1287
- Source
- security-advisories@github.com
EPSS moved from 0.4% on 9 October 2026 to 0.5% on 26 October 2026.
References
- https://github.com/nearform/fast-jwt/commit/86e83efd8b5244f50859532d99244f0a9a9a4368
- https://github.com/nearform/fast-jwt/pull/639
- https://github.com/nearform/fast-jwt/releases/tag/v6.3.0
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-5hjw-83fp-phq9
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-5hjw-83fp-phq9
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.