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CVE-2026-34240

HIGH CVSS 3.1: 7.5 EPSS 0.01%
Updated Apr 06, 2026
Appsup-Dart
Parameter Value
CVSS 7.5 (HIGH)
Affected Versions before 0.3.5\+1
Fixed In 0.3.5
Type CWE-347 (Improper Verification of Cryptographic Signature)
Vendor Appsup-Dart
Public PoC No

JOSE is a Javascript Object Signing and Encryption (JOSE) library. Prior to version 0.3.5+1, a vulnerability in jose could allow an unauthenticated, remote attacker to forge valid JWS/JWT tokens by using a key embedded in the JOSE header (jwk). The vulnerability exists because key selection could treat header-provided jwk as a verification candidate even when that key was not present in the trusted key store.

Since JOSE headers are untrusted input, an attacker could exploit this by creating a token payload, embedding an attacker-controlled public key in the header, and signing with the matching private key. Applications using affected versions for token verification are impacted. This issue has been patched in version 0.3.5+1.

A workaround for this issue involves rejecting tokens where header jwk is present unless that jwk matches a key already present in the application's trusted key store.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
None
No data leak
Integrity
High
Complete data modification
Availability
None
No disruption

CVSS Vector v3.1

Vulnerable Products 1

Configuration From (including) Up to (excluding)
Appsup-Dart Jose
cpe:2.3:a:appsup-dart:jose:*:*:*:*:*:*:*:*
0.3.5\+1