CVE-2026-9800 in Keycloak
Summary
by MITRE • 06/25/2026
A flaw was found in Keycloak Policy Enforcer. This vulnerability allows any authenticated user to bypass all authorization policies, including role, scope, and User-Managed Access (UMA) permission checks. By including the configured access-denied page path within a request URL, either as a path segment or a query parameter, an attacker can gain unauthorized access to protected resources.
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Analysis
by VulDB Data Team • 06/26/2026
This vulnerability in Keycloak Policy Enforcer represents a critical authorization bypass flaw that fundamentally undermines the security controls designed to protect enterprise applications. The issue stems from improper validation of access-denied page paths within request URLs, allowing authenticated users to manipulate their requests and circumvent all authorization policies. The flaw exists at the core of Keycloak's policy enforcement mechanism where the system fails to properly distinguish between legitimate access-denied redirects and malicious attempts to bypass authorization checks.
The technical implementation of this vulnerability leverages the way Keycloak processes URL paths and query parameters during authentication flows. When an authenticated user makes a request to a protected resource, the system should validate whether the user possesses the necessary permissions based on roles, scopes, or UMA permissions. However, the flaw allows attackers to include the configured access-denied page path either as a path segment or query parameter within their request, effectively tricking the policy enforcer into treating the request as an authorized access attempt. This occurs because the system does not properly sanitize or validate these paths before processing authorization decisions.
The operational impact of this vulnerability is severe and far-reaching across enterprise security environments that rely on Keycloak for identity and access management. Any authenticated user, regardless of their actual permissions or roles, can gain unauthorized access to protected resources that should only be available to specific users or groups. This affects not just traditional role-based access control but also scope-based authorization and User-Managed Access permissions, creating a complete breakdown in the authorization framework. The vulnerability essentially provides a backdoor that bypasses all security controls implemented within Keycloak's policy enforcement layer.
Organizations using Keycloak for securing applications face significant risks including data breaches, unauthorized access to sensitive information, and potential lateral movement within their network infrastructure. The vulnerability affects any application that uses Keycloak as its identity provider and relies on the built-in policy enforcer for access control decisions. This includes web applications, microservices, and API gateways that depend on Keycloak's authorization mechanisms.
The vulnerability aligns with CWE-285 which addresses improper authorization issues in software systems, specifically targeting the failure to properly enforce access controls. From an ATT&CK framework perspective, this represents a privilege escalation technique where attackers leverage authentication bypasses to gain elevated access rights. Organizations should immediately implement mitigations including updating to patched versions of Keycloak, reviewing all access-denied page configurations, and implementing additional monitoring for unusual URL patterns that might indicate exploitation attempts.
Security teams should also consider implementing network-level controls to detect and block requests containing suspicious access-denied page path patterns, while conducting comprehensive audits of existing authorization policies to identify any potential unauthorized access that may have occurred during the vulnerability's active period. The fix typically involves strengthening input validation mechanisms within Keycloak's policy enforcement module to ensure that access-denied page paths are properly sanitized and validated before being processed in authorization decisions.