CVE-2026-75509
Medium
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.
SeverityMedium
CVSS6.5
Exploit probability—
ProductAuthlib Joserfc
PublishedAug 24, 2026
First seenAug 24, 2026
Weakness typeCWE-290CWE-290CWE-345CWE-345
How to fix
Sources list no fixed version or patch link for this vulnerability.
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| authlib joserfc | < 1.7.3 | — |
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