---
id: CVE-2026-18203
title: >-
  A flaw was found in the group policy evaluation logic of Keycloak, an identity
  and access management solution
summary: >-
  A flaw was found in the group policy evaluation logic of Keycloak, an identity
  and access management solution. When a group policy is set to extend
  permissions to child groups, the system incorrectly uses a simple text-based
  prefix check…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-863
published: '2026-07-31'
updated: '2026-08-01'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-18203'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-18203'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2508291'
    label: secalert@redhat.com
tags:
  - nvd
epss: 0.00312
epssPercentile: 0.21423
ingestedAt: '2026-08-01T23:16:02.146Z'
---

## Overview

A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to a different group with a similar starting name to bypass security checks and gain unauthorized access to administrative functions or protected resources.

## Remediation

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