Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-28T13:44:55 keycloak-services: keycloak-services: Group policy extendChildren matches sibling group path prefixes 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N CWE-863

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.

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.

The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires a specific group naming collision and the extendChildren policy setting to be active. Successful exploitation allows an attacker to gain unauthorized integrity-impacting permissions within the realm. The vulnerability's root cause is an improper string prefix comparison during group path validation in the authorization services. Red Hat would like to thank Paul Bottinelli (Trail of Bits) for reporting this issue. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Red Hat Build of Keycloak Affected keycloak-services Red Hat Build of Keycloak Affected rhbk-keycloak-rhel9/rhbk-keycloak-rhel9 Red Hat Build of Keycloak Affected rhbk-openshift-rhel9/rhbk-openshift-rhel9 Red Hat Data Grid 8 Not affected keycloak-services Red Hat JBoss Enterprise Application Platform Expansion Pack Not affected keycloak-services Red Hat Single Sign-On 7 Not affected keycloak-services https://www.cve.org/CVERecord?id=CVE-2026-18203 https://nvd.nist.gov/vuln/detail/CVE-2026-18203