{"id":"CVE-2026-35039","aliases":["GHSA-rp9m-7r4c-75qg"],"url":"https://o3.security/vulnerability/CVE-2026-35039","summary":"fast-jwt Affected by Cache Confusion via cacheKeyBuilder Collisions Can Return Claims From a Different Token (Identity/Authorization Mixup)","details":"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.","published":"2026-04-06T16:59:43.124Z","modified":"2026-08-12T03:51:26.964315352Z","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":{"score":0.00212,"percentile":0.11364,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"fast-jwt","fixedVersion":"6.2.0"}],"fix":{"url":"https://github.com/nearform/fast-jwt/commit/de121056c6415b58770c60640881eaec67ac4ceb","label":"nearform/fast-jwt@de12105"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/35xxx/CVE-2026-35039.json"},{"type":"ADVISORY","url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-rp9m-7r4c-75qg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-35039"},{"type":"FIX","url":"https://github.com/nearform/fast-jwt/commit/de121056c6415b58770c60640881eaec67ac4ceb"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:26.964315352Z"}}