CVE-2026-35041
ReDoS in fast-jwt when using RegExp in allowed* leading to CPU exhaustion during token verification
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
fast-jwt provides fast JSON Web Token (JWT) implementation. From 5.0.0 to 6.2.0, a denial-of-service condition exists in fast-jwt when the allowedAud verification option is configured using a regular expression. Because the aud claim is attacker-controlled and the library evaluates it against the supplied RegExp, a crafted JWT can trigger catastrophic backtracking in the JavaScript regex engine, resulting in significant CPU consumption during verification. This vulnerability is fixed in 6.2.1.
Public exploit
A reference of the record is tagged as an exploit or proof of concept: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: a proof of concept is public.
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4-fwxf (opens in a new tab)x_refsource_CONFIRMexploit
Timeline
ID reserved
By GitHub_M
- 9 days later
· 9 days later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium4.2 | CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H |
| NVDNVD · Analyzed | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.27% · top 80% of all CVEs (8 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.2.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- npmfast-jwtGHSA-cjw9-ghj4-fwxf (opens in a new tab)
References (4)
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4-fwxf (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/nearform/fast-jwt/pull/595 (opens in a new tab)x_refsource_MISC
- https://github.com/nearform/fast-jwt/commit/b0be0ca161593836a153d5180ca5358ad9b5de94 (opens in a new tab)x_refsource_MISC
- https://github.com/nearform/fast-jwt/releases/tag/v6.2.1 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-cjw9-ghj4-fwxf (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-35041)Record last updated .