CVE-2026-34950 — fast-jwt has an incomplete fix for CVE-2023-48223: JWT Algorithm Confusion via Whitespace-Prefixed RSA Public Key

CVE-2026-34950

fast-jwt has an incomplete fix for CVE-2023-48223: JWT Algorithm Confusion via Whitespace-Prefixed RSA Public Key PUBLISHED

Description (CNA)

fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, the publicKeyPemMatcher regex in fast-jwt/src/crypto.js uses a ^ anchor that is defeated by any leading whitespace in the key string, re-enabling the exact same JWT algorithm confusion attack that CVE-2023-48223 patched.

Affected (CNA)

Vendor / product	Versions
nearform / fast-jwt	affected <= 6.1.0

CWE

CWE-327

References

https://github.com/nearform/fast-jwt/security/advisories/GHSA-mvf2-f6gm-w987

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.