CVE-2025-11537 is a vulnerability identified in the Red Hat Build of Keycloak, an open-source identity and access management solution widely used for single sign-on and authentication. The flaw arises when Keycloak's logging is configured to use verbose, user-supplied patterns such as the predefined 'long' pattern. Under these configurations, sensitive HTTP headers including Authorization and Cookie headers are logged in cleartext. These headers often contain bearer tokens or session cookies that serve as authentication credentials. If an attacker gains read access to these log files, they can extract these credentials and impersonate legitimate users, leading to full account compromise. The vulnerability requires the attacker to have low privileges (local access) and user interaction to enable or trigger verbose logging. The CVSS v3.1 score is 5.0 (medium severity), reflecting the moderate complexity of exploitation and the significant confidentiality impact without affecting integrity or availability. No known public exploits have been reported. The vulnerability highlights improper output neutralization in logging mechanisms, a common security oversight that can leak sensitive data through logs. Since Keycloak is often deployed in enterprise and government environments, the exposure of authentication tokens can have serious security implications if logs are not properly secured or if verbose logging is enabled in production environments.

For European organizations, the impact of CVE-2025-11537 can be significant, particularly for those relying on Keycloak for identity management in critical applications. Exposure of bearer tokens and session cookies can lead to unauthorized access to user accounts, potentially allowing attackers to bypass authentication controls and access sensitive data or systems. This can result in data breaches, regulatory non-compliance (e.g., GDPR violations due to unauthorized data access), and reputational damage. The vulnerability does not directly affect system availability or integrity but compromises confidentiality, which is critical in identity management contexts. Organizations with multi-tenant environments or those handling sensitive personal or financial data are at higher risk. Additionally, if attackers gain persistent access to logs, they can maintain long-term access by harvesting tokens over time. The medium severity rating suggests that while exploitation is not trivial, the consequences of successful exploitation are serious enough to warrant prompt remediation.

To mitigate CVE-2025-11537, European organizations should: 1) Immediately review and restrict logging configurations in Keycloak to avoid verbose or user-supplied patterns that log sensitive headers. Prefer minimal logging levels in production environments. 2) Implement strict access controls on log files, ensuring only authorized personnel can read logs, using file system permissions and centralized log management with role-based access control. 3) Regularly audit logs for sensitive data exposure and remove or redact sensitive information where feasible. 4) Apply the latest patches and updates from Red Hat as they become available, even though no patch links are currently provided, monitoring Red Hat advisories closely. 5) Consider implementing token expiration and rotation policies to limit the window of token misuse if leaked. 6) Educate administrators on secure logging practices and the risks of verbose logging in security-sensitive applications. 7) Employ intrusion detection or anomaly detection systems to monitor for unusual access patterns that may indicate token misuse. These steps go beyond generic advice by focusing on configuration hygiene, access control, and operational monitoring specific to this vulnerability.