A flaw was found in the client policy enforcement mechanism of Keycloak. The issue occurs when the system checks group membership by name instead of a unique identifier. An attacker with client management privileges could bypass security policies by joining a group with a matching name in a different part of the group hierarchy, potentially allowing them to register or update clients without following required security hardening profiles.

The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires the attacker to have existing client registration or update privileges and a specific group hierarchy configuration. Successful exploitation allows an attacker to bypass client policy enforcement and register or update clients without required security hardening. The vulnerability's root cause is the use of non-unique group names for membership validation in client policy conditions. 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-2026-18207 https://nvd.nist.gov/vuln/detail/CVE-2026-18207