Description
fast-jwt provides fast JSON Web Token (JWT) implementation. From 0.0.1 to before 6.2.0, setting up a custom cacheKeyBuilder method which does not properly create unique keys for different tokens can lead to cache collisions. This could cause tokens to be mis-identified during the verification process leading to valid tokens returning claims from different valid tokens and users being mis-identified as other users based on the wrong token. Version 6.2.0 contains a patch.
Affected products
nearform: fast-jwt
References2
- github.com/nearform/fast-jwt/security/advisories/GHSA-rp9m-7r4c… MitigationVendor Advisory
- github.com/nearform/fast-jwt/commit/de121056c6415b58770c6064088… Patch
Metrics
- CVSS 3.1
-
9.1
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - EPSS — exploit probability
- 0% percentile: 12 · as of 12 November 2026
- CWE
- CWE-345CWE-706CWE-1289
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.