fast-jwt: Stateful RegExp (/g or /y) causes non-deterministic allowed-claim validation (logical DoS)

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.0038, the 32nd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the GitHub Advisory Database, published 9 Apr 2026. New records show when each source confirmed them.

Sources

• GitHub Advisory Database: GHSA-3j8v-cgw4-2g6q
• OSV: GHSA-3j8v-cgw4-2g6q
• github.com/nearform/fast-jwt/security/advisories/GHSA-3j8v-cgw4-2g6q
• nvd.nist.gov/vuln/detail/CVE-2026-35040
• github.com/nearform/fast-jwt/pull/593
• github.com/nearform/fast-jwt/commit/18d25904e4617e8753526d1b3ab5a2cccdea726a
• github.com/nearform/fast-jwt
• github.com/nearform/fast-jwt/releases/tag/v6.2.1

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.