CVE-2018-14637 in KeyCloak
Summary
by MITRE
The SAML broker consumer endpoint in Keycloak before version 4.6.0.Final ignores expiration conditions on SAML assertions. An attacker can exploit this vulnerability to perform a replay attack.
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Analysis
by VulDB Data Team • 06/12/2023
The vulnerability identified as CVE-2018-14637 resides within the SAML broker consumer endpoint implementation of Keycloak authentication platform, specifically affecting versions prior to 4.6.0.Final. This represents a critical security flaw that undermines the fundamental integrity of SAML-based authentication mechanisms by failing to properly validate assertion expiration timestamps. The issue manifests when Keycloak processes SAML assertions through its broker consumer endpoint, where the system neglects to enforce the expiration conditions that are inherently part of the SAML protocol specification. This oversight creates a persistent security weakness that allows malicious actors to exploit the absence of time-based validation controls.
The technical flaw stems from the improper handling of SAML assertion lifetime parameters within Keycloak's authentication flow. SAML assertions contain built-in expiration timestamps that define the valid time window during which the assertion remains acceptable for authentication purposes. When Keycloak's broker consumer endpoint fails to validate these expiration conditions, it effectively accepts assertions that have already expired, thereby bypassing critical temporal security controls. This behavior directly violates the core principles of authentication security where time-bound validation serves as a fundamental defense against replay attacks and session hijacking attempts. The vulnerability operates at the protocol level where Keycloak should be enforcing the SAML standard's requirement for assertion expiration validation but instead silently accepts outdated assertions.
The operational impact of this vulnerability extends far beyond simple authentication bypass scenarios, creating significant risks for organizations relying on Keycloak for identity management and single sign-on services. Attackers can exploit this weakness to conduct successful replay attacks by capturing valid SAML assertions and reusing them after their intended expiration time has passed. This capability undermines the entire authentication trust model, as it allows unauthorized access to protected resources through the reuse of previously valid authentication tokens. The vulnerability particularly affects environments where Keycloak serves as a central identity provider or broker for multiple applications, amplifying the potential damage from a single compromised assertion. Organizations may experience unauthorized access to sensitive systems, data breaches, and violations of compliance requirements that mandate proper session management and authentication validation.
Mitigation strategies for CVE-2018-14637 require immediate patching of Keycloak installations to version 4.6.0.Final or later, which includes the necessary fixes to properly validate SAML assertion expiration conditions. System administrators should also implement additional monitoring controls to detect unusual authentication patterns that might indicate replay attack attempts. The fix addresses the underlying CWE-295 vulnerability category related to improper certificate validation and weak session management, aligning with ATT&CK technique T1566.002 for credential access through SAML-based attacks. Organizations should also consider implementing additional security controls such as assertion signing verification, session timeout enforcement, and regular security audits of their identity federation configurations to prevent similar vulnerabilities from emerging in other components of their authentication infrastructure.