CVE-2026-75509

MEDIUM CVSS 3.1: 6.5
Updated Aug 24, 2026
Python
Parameter Value
CVSS 6.5 (MEDIUM)
Fixed In 1.7.3
Type CWE-290, CWE-345 (Insufficient Verification of Data)
Vendor Python
Public PoC No

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to version 1.7.3, JWTClaimsRegistry applies membership matching to list-valued iss and sub claims, allowing an array-valued iss that contains the expected issuer to pass an intended equality check and enabling issuer-validation bypass. This issue is fixed in version 1.7.3.

Attack Parameters

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

Impact Assessment

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

CVSS Vector v3.1