---
id: CVE-2026-75509
title: >-
  joserfc is a Python library that provides an implementation of several JSON
  Object Signing and Encryption (JOSE) standards
summary: >-
  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…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N'
cwe:
  - CWE-290
  - CWE-345
  - CWE-480
published: '2026-08-24'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T15:10:00.207'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-75509'
references:
  - url: >-
      https://github.com/authlib/joserfc/commit/76ee6a59bf5773c0af00b99076c5e199031f97f1
    label: security-advisories@github.com
  - url: 'https://github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpj'
    label: security-advisories@github.com
  - url: 'https://github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpj'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-75509.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-75509'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2523102'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-75509'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-75509'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
epss: 0.00124
epssPercentile: 0.02126
ingestedAt: '2026-09-09T21:22:45.549Z'
vendor: Red Hat
product: Red Hat Ansible Automation Platform 2
affected:
  - lightspeed_core
  - migration_toolkit_for_applications 8
  - openshift_lightspeed
  - ansible_automation_platform 2
  - enterprise_linux_command_line_assistant
  - openshift_virtualization 4
  - satellite 6
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Lightspeed Core, Migration Toolkit for Applications 8, OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux command line assistant, Red Hat OpenShift Virtualization 4, … · no fix planned: Lightspeed Core, Migration Toolkit for Applications 8, OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, … · updated 2026-10-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-75509.json)