Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-28T12:12:27 keycloak-services: keycloak-services: Microsoft external access-token exchange bypasses configured tenant 6.8 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N CWE-287

Keycloak provides a way to let users log in using Microsoft accounts while restricting access to a specific organization (tenant). A flaw was discovered where this restriction is ignored when using the token exchange feature. This means an attacker with a valid Microsoft token from a completely different organization could gain access to the Keycloak realm, potentially accessing sensitive data or performing unauthorized actions.

Keycloak provides a way to let users log in using Microsoft accounts while restricting access to a specific organization (tenant). A flaw was discovered where this restriction is ignored when using the token exchange feature. This means an attacker with a valid Microsoft token from a completely different organization could gain access to the Keycloak realm, potentially accessing sensitive data or performing unauthorized actions.

The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires the attacker to possess a valid Microsoft Graph access token from a different tenant. Successful exploitation allows an attacker to bypass configured tenant restrictions and gain unauthorized access to a Keycloak realm. The vulnerability's root cause is the lack of tenant ID verification during the external access-token exchange flow when interacting with the Microsoft Graph API. 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-2026-18215 https://nvd.nist.gov/vuln/detail/CVE-2026-18215