CVE-2026-34950

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.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/nearform/fast-jwt/security/advisories/GHSA-mvf2-f6gm-w987	Exploit Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:nearform:fast-jwt:*:*:*:*:*:node.js:*:*

History

26 Oct 2026, 21:10

Type	Values Removed	Values Added
Summary		(es) fast-jwt proporciona una implementación rápida de JSON Web Token (JWT). En la versión 6.1.0 y anteriores, la expresión regular publicKeyPemMatcher en fast-jwt/src/crypto.js utiliza un anclaje ^ que es anulado por cualquier espacio en blanco inicial en la cadena de clave, reactivando el mismo ataque de confusión de algoritmo JWT que CVE-2023-48223 parcheó.

Information

Published : 2026-04-06 16:16

Updated : 2026-10-26 21:10

NVD link : CVE-2026-34950

Mitre link : CVE-2026-34950

CVE.ORG link : CVE-2026-34950

JSON object : View

Products Affected

nearform

fast-jwt

CWE

CWE-327

Use of a Broken or Risky Cryptographic Algorithm

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