CVE-2026-34950

Severity CVSS v4.0:

Pending analysis

Type:

CWE-327 Use of a Broken or Risky Cryptographic Algorithm

Publication date:

06/04/2026

Last modified:

06/04/2026

Description

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.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N CVSS v3.1 Severity and Metrics:

Base Score: 9.10 CRITICAL
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): High
Integrity (I): High
Availability (A): None

Base Score 3.x

9.10

Severity 3.x

CRITICAL

References to Advisories, Solutions, and Tools

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