CVE-2026-75509CWE-290CWE-345

CVE-2026-75509

Medium · published August 25, 2026

CVSS v3.1
6.5
EPSS
0%
Percentile
2.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.5 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00124 · 2.0th percentile
Weaknesses
CWE-290 · Authentication Bypass by Spoofing; CWE-345 · Insufficient Verification of Data Authenticity
Published
2026-08-25T00:17Z
References (3)
https://github.com/authlib/joserfc/commit/76ee6a59bf5773c0af00b99076c5e199031f97f1 · [email protected]https://github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpj · [email protected]https://github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpj · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 26 AUG 08:27Z
    EPSS moved — → 0%
    epss
  • 24 AUG 20:08Z
    joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)
    cvelistv5