CVE-2026-2366 is an authorization bypass vulnerability identified in the Red Hat build of Keycloak version 26.4. The flaw resides in the Admin API, specifically affecting the Organizations feature. An authenticated user, even without administrative privileges, can exploit this vulnerability to enumerate the organization memberships of other users if they know the victim's unique identifier (UUID). This means that an attacker can retrieve information about which organizations a user belongs to, potentially exposing sensitive organizational structure or membership data. The vulnerability does not allow modification or deletion of data, nor does it affect system availability, limiting the impact to confidentiality. The attack requires the attacker to be authenticated and to know the victim's UUID, which raises the attack complexity. The CVSS v3.1 base score is 3.1, reflecting a low severity due to limited confidentiality impact and higher attack complexity. There are no known exploits in the wild at the time of publication. The vulnerability highlights a design weakness in access control enforcement within the Admin API when handling organization membership queries. Since the Organizations feature must be enabled for this issue to be exploitable, environments not using this feature are not affected. No patches or fixes are currently linked, so mitigation may rely on configuration changes or monitoring until a fix is released.

The primary impact of CVE-2026-2366 is limited information disclosure regarding user organization memberships within Keycloak deployments. For organizations, this could lead to exposure of internal organizational structures or membership details, which might aid attackers in reconnaissance or social engineering attacks. While the vulnerability does not allow privilege escalation, data modification, or denial of service, the leakage of membership information could be sensitive in environments where organizational affiliations are confidential or where such information could be leveraged for targeted attacks. The requirement for authentication and knowledge of victim UUID limits the scope of exploitation, reducing the risk of widespread automated attacks. However, in large enterprises or service providers using Keycloak for identity and access management, this vulnerability could be exploited by insiders or compromised accounts to gather intelligence on other users. The absence of known exploits reduces immediate risk, but the vulnerability should be addressed promptly to prevent potential misuse.

To mitigate CVE-2026-2366, organizations should first verify whether the Organizations feature in Keycloak is enabled and assess the necessity of this feature. If not required, disabling the Organizations feature can eliminate the attack surface. For environments where the feature is essential, strict access controls should be enforced to limit authenticated user permissions and prevent unnecessary access to the Admin API endpoints. Monitoring and logging of Admin API access should be enhanced to detect unusual enumeration patterns or access attempts involving user UUIDs. Organizations should implement strong authentication mechanisms to reduce the risk of compromised accounts being used to exploit this vulnerability. Until an official patch or update is released by Red Hat, consider applying custom API gateway rules or filters to restrict access to organization membership enumeration endpoints. Regularly review Keycloak release notes and security advisories for patches addressing this issue and apply updates promptly. Additionally, educate users and administrators about the risk of sharing UUIDs or other identifiers that could facilitate exploitation.