CVE-2026-75509
joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)
Description
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.
INFO
Published Date :
Aug. 24, 2026, 8:17 p.m.
Last Modified :
Aug. 24, 2026, 8:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-75509
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update the joserfc library to version 1.7.3 or later.
- Verify JWT issuer validation is functioning correctly.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-75509.
| URL | Resource |
|---|---|
| https://github.com/authlib/joserfc/commit/76ee6a59bf5773c0af00b99076c5e199031f97f1 | |
| https://github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpj |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-75509 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-75509
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-75509 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-75509 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Aug. 24, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'authlib', 'product': 'joserfc', 'versions': [{'status': 'affected', 'version': '< 1.7.3'}]}] Added Description 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. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N Added CWE CWE-345 Added CWE CWE-290 Added Reference https://github.com/authlib/joserfc/commit/76ee6a59bf5773c0af00b99076c5e199031f97f1 Added Reference https://github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpj