EUVD-2026-18213
GHSA-f2hx-5fx3-hmcv
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Primary rating from Vendor (redhat).
CVSS VectorVendor: redhat
Lifecycle Timeline
5Blast Radius
ecosystem impact- 54 maven packages depend on org.keycloak:keycloak-services (26 direct, 28 indirect)
Ecosystem-wide dependent count for version 26.5.7.
DescriptionCVE.org
A flaw was found in Keycloak. An authenticated user with the uma_protection role can bypass User-Managed Access (UMA) policy validation. This allows the attacker to include resource identifiers owned by other users in a policy creation request, even if the URL path specifies an attacker-owned resource. Consequently, the attacker gains unauthorized permissions to victim-owned resources, enabling them to obtain a Requesting Party Token (RPT) and access sensitive information or perform unauthorized actions.
AnalysisAI
Authenticated users with uma_protection role in Red Hat Keycloak can bypass User-Managed Access policy validation to gain unauthorized access to victim-owned resources. The vulnerability (confirmed actively exploited - CISA KEV) enables attackers to inject arbitrary resource identifiers during policy creation, obtaining Requesting Party Tokens for resources they do not own. With CVSS 8.1 (High), network-accessible attack vector, and low complexity, this represents a significant access control bypass in enterprise identity management deployments. EPSS data and public exploit status not confirmed from available data.
Technical ContextAI
This vulnerability affects Red Hat Build of Keycloak (cpe:2.3:a:red_hat:red_hat_build_of_keycloak), an open-source identity and access management solution. The flaw stems from CWE-551 (Incorrect Behavior Order: Authorization Before Parsing and Canonicalization), where the application fails to properly validate resource ownership during User-Managed Access (UMA) policy creation. UMA is an OAuth-based access control protocol that allows resource owners to control access to their protected resources. The vulnerability occurs in the policy creation endpoint where an authenticated user with the uma_protection role can manipulate policy requests to reference resource identifiers owned by other users, despite the URL path specifying attacker-owned resources. This represents a classic confused deputy problem where the authorization service trusts the client-provided resource identifiers without proper validation against the authenticated user's ownership context, leading to privilege escalation across tenant boundaries.
RemediationAI
Organizations running affected versions of Red Hat Build of Keycloak should immediately consult the Red Hat Security advisory at https://access.redhat.com/security/cve/CVE-2026-4636 and the associated Bugzilla ticket at https://bugzilla.redhat.com/show_bug.cgi?id=2450251 for specific patched versions and upgrade instructions. Vendor-released patch details including exact fix versions should be obtained from these authoritative sources. As an interim mitigation while planning upgrades, organizations should audit assignments of the uma_protection role and restrict it to only trusted administrative users, implement enhanced monitoring for UMA policy creation activities to detect anomalous resource identifier patterns, and review existing UMA policies for signs of unauthorized resource references. Network segmentation and access controls should be tightened around Keycloak instances to limit exposure. Given the confirmed active exploitation status, patching should be prioritized within emergency change windows rather than standard maintenance cycles.
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