CVE-2018-10912 in KeyCloak
Summary
by MITRE
keycloak before version 4.0.0.final is vulnerable to a infinite loop in session replacement. A Keycloak cluster with multiple nodes could mishandle an expired session replacement and lead to an infinite loop. A malicious authenticated user could use this flaw to achieve Denial of Service on the server.
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Analysis
by VulDB Data Team • 04/25/2023
The vulnerability identified as CVE-2018-10912 affects Keycloak versions prior to 4.0.0.final and represents a critical denial of service flaw within the authentication server's session management mechanism. This vulnerability specifically targets the session replacement functionality within Keycloak clusters that operate across multiple nodes, creating a scenario where the system can become trapped in an infinite loop under specific conditions. The flaw manifests when an expired session replacement operation is mishandled by the cluster infrastructure, leading to a cascading failure that can bring the affected server to its knees.
The technical implementation of this vulnerability stems from improper handling of session lifecycle events within distributed Keycloak deployments. When multiple cluster nodes attempt to process an expired session replacement simultaneously, the system enters a condition where session validation logic repeatedly attempts to replace the same session without proper termination conditions. This creates a pathological state where the session management subsystem continuously loops through replacement operations, consuming excessive CPU resources and preventing legitimate authentication requests from being processed. The vulnerability is particularly dangerous in clustered environments where session state must be synchronized across multiple nodes, as the infinite loop can propagate throughout the entire cluster infrastructure.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of authentication services for all users within the affected Keycloak deployment. An authenticated malicious user can exploit this flaw by initiating specific session replacement sequences that trigger the infinite loop condition, effectively creating a denial of service attack against the Keycloak server. This attack vector is particularly concerning because it requires only authenticated access, making it accessible to users who have already established credentials within the system. The resource exhaustion caused by the infinite loop can lead to complete service unavailability, preventing legitimate users from accessing protected applications and services that depend on Keycloak for authentication.
Organizations utilizing Keycloak in clustered configurations should prioritize immediate remediation of this vulnerability through version upgrades to 4.0.0.final or later releases. The fix implemented in version 4.0.0.final addresses the root cause by introducing proper loop detection and termination mechanisms within the session replacement logic, ensuring that expired session operations complete successfully without entering infinite loops. Additional mitigations include implementing proper session timeout configurations, monitoring for unusual CPU usage patterns, and establishing alerting mechanisms to detect potential exploitation attempts. From a security framework perspective, this vulnerability aligns with CWE-835, which addresses infinite loops in software systems, and represents a significant concern within the ATT&CK framework under the denial of service category, specifically targeting the availability of authentication services. The vulnerability demonstrates the critical importance of proper session management in distributed systems and highlights the need for comprehensive testing of session lifecycle operations in clustered environments to prevent similar issues from arising in other security frameworks.