CVE-2026-9099 in Keycloak
Summary
by MITRE • 06/25/2026
A flaw was found in Keycloak. A missing authorization check in the GroupResource.addChild() endpoint within the Admin REST API allows an authenticated user with limited administrative privileges to reparent any existing group. When Fine-Grained Admin Permissions v2 (FGAPv2) is enabled, an attacker with management rights over a single low-privilege group can reparent a highly privileged group (such as one possessing the realm-admin role) under their managed group.
Because group permissions follow a hierarchical structure, this action unauthorizedly grants the attacker management and password-reset capabilities over the members of the targeted privileged group. An attacker can exploit this to reset an administrator's password, compromise the account, and achieve a full realm takeover, leading to a complete compromise of confidentiality, integrity, and availability.
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Analysis
by VulDB Data Team • 06/25/2026
This vulnerability exists within the Keycloak identity and access management platform where a critical authorization flaw has been identified in the GroupResource.addChild() endpoint of the Admin REST API. The issue stems from a missing authorization check that allows authenticated users with limited administrative privileges to manipulate group hierarchies regardless of their actual permissions. This represents a significant security weakness that directly violates the principle of least privilege and proper access control mechanisms.
The technical implementation flaw occurs when Fine-Grained Admin Permissions v2 (FGAPv2) is enabled, creating a dangerous condition where attackers can leverage their management rights over one low-privilege group to gain unauthorized control over highly privileged groups. The vulnerability specifically affects the hierarchical group permission model where group membership and management rights follow a tree-like structure. When an attacker successfully reparents a privileged group under their controlled group, they inherit the administrative capabilities of that privileged group.
The operational impact of this vulnerability is severe and far-reaching within Keycloak environments. An attacker who can exploit this flaw can escalate their privileges significantly by gaining management and password-reset capabilities over members of targeted privileged groups. This capability enables attackers to reset administrator passwords, compromise accounts, and ultimately achieve complete control over the entire realm. The vulnerability essentially allows for privilege escalation from limited administrative rights to full realm administration, creating a pathway for complete system compromise.
This vulnerability maps directly to CWE-863 (Incorrect Authorization) which specifically addresses situations where authorization checks are missing or incorrectly implemented. From an ATT&CK framework perspective, this represents a privilege escalation technique that leverages the group hierarchy to move laterally within the access control system. The attack chain typically involves initial authentication with limited privileges followed by exploitation of the authorization gap to gain broader administrative capabilities.
Mitigation strategies should focus on immediate patching of the Keycloak platform to address the missing authorization check in the GroupResource.addChild() endpoint. Organizations should also implement additional monitoring for unauthorized group rehierarchization events and consider disabling FGAPv2 if it is not essential for operations. Network segmentation and least privilege enforcement should be reviewed to minimize potential damage from successful exploitation attempts, while regular security audits of group permissions and access control configurations should be conducted to detect and prevent similar vulnerabilities.