CVE-2026-18207 in Keycloak
Summary
by MITRE • 07/29/2026
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.
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Analysis
by VulDB Data Team • 07/29/2026
This vulnerability resides within Keycloak's client policy enforcement framework where the system incorrectly validates group membership through name comparison rather than unique identifier verification. The flaw represents a classic authorization bypass issue that undermines the integrity of access control mechanisms by exploiting the ambiguity inherent in group naming conventions across hierarchical structures. When an attacker possesses client management privileges, they can manipulate group assignments to circumvent security policies that should restrict client registration and update operations based on predefined hardening profiles.
The technical implementation defect stems from a failure to enforce unique identifier validation during group membership checks, creating a path where attackers can exploit the system's reliance on potentially non-unique group names. This vulnerability directly maps to CWE-285, which addresses improper authorization in authentication systems, and aligns with ATT&CK technique T1078.101 focusing on valid accounts for privilege escalation. The flaw operates by allowing an attacker to create or join a group with the same name as a restricted group within a different hierarchy level, effectively bypassing the intended policy enforcement mechanisms that should prevent unauthorized client modifications.
The operational impact of this vulnerability extends beyond simple privilege escalation to compromise the overall security posture of Keycloak implementations. Organizations using this authentication platform face potential exposure where attackers can register malicious clients or modify existing ones without adhering to established security profiles, potentially leading to unauthorized access points, data exfiltration capabilities, or lateral movement opportunities within the authenticated environment. The vulnerability particularly affects systems that rely heavily on group-based access control and policy enforcement for client management operations.
Mitigation strategies should focus on implementing robust unique identifier validation mechanisms throughout the group membership verification process, ensuring that all group references are validated against unique identifiers rather than potentially ambiguous names. Organizations must also enforce stricter access controls for client management privileges, implement comprehensive audit logging of group membership changes, and consider adopting automated tools to identify and remediate duplicate group names across hierarchies. Additionally, regular security assessments should validate that policy enforcement mechanisms properly distinguish between different group contexts to prevent similar authorization bypass scenarios from occurring in other components of the authentication infrastructure.