CVE-2011-1528 in Kerberos
Summary
by MITRE
The krb5_ldap_lockout_audit function in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.8 through 1.8.4 and 1.9 through 1.9.1, when the LDAP back end is used, allows remote attackers to cause a denial of service (assertion failure and daemon exit) via unspecified vectors, related to the locked_check_p function. NOTE: the Berkeley DB vector is covered by CVE-2011-4151.
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Analysis
by VulDB Data Team • 08/04/2024
The vulnerability identified as CVE-2011-1528 represents a critical denial of service weakness within the MIT Kerberos 5 implementation that affects specific version ranges including 1.8 through 1.8.4 and 1.9 through 1.9.1 when utilizing the LDAP backend for authentication services. This flaw resides within the krb5_ldap_lockout_audit function of the Key Distribution Center component, which serves as the central authentication authority for kerberos networks. The vulnerability manifests when the system processes authentication requests through LDAP backends, creating a scenario where remote attackers can trigger system instability through unspecified attack vectors that ultimately lead to assertion failures and complete daemon termination.
The technical root cause of this vulnerability stems from inadequate input validation and error handling within the locked_check_p function that operates in conjunction with the LDAP backend implementation. When processing authentication requests, the system fails to properly validate certain parameters or states that could arise during concurrent authentication attempts or when dealing with locked account conditions. This failure results in an assertion that evaluates to false, causing the daemon to terminate abruptly rather than gracefully handling the exceptional condition. The flaw demonstrates characteristics consistent with CWE-617, which addresses reachable assertions, and represents a classic example of improper error handling that can be exploited to create denial of service conditions.
The operational impact of CVE-2011-1528 extends beyond simple service interruption as it directly affects the core authentication infrastructure of systems relying on MIT Kerberos 5 with LDAP backends. When the KDC daemon crashes due to this vulnerability, it completely disrupts authentication services for all clients within the kerberos realm, potentially affecting hundreds or thousands of users depending on the scale of the deployment. Organizations using this vulnerable configuration face significant operational risks including business continuity disruptions, authentication failures across enterprise applications, and potential cascading effects on dependent services that rely on kerberos authentication. The vulnerability is particularly dangerous because it allows remote exploitation without requiring authentication credentials, making it an attractive target for malicious actors seeking to disrupt services.
Mitigation strategies for CVE-2011-1528 primarily focus on immediate version upgrades to patched releases of MIT Kerberos 5, specifically versions that contain fixes for the LDAP backend assertion handling issues. Organizations should prioritize updating their kerberos implementations to versions that have addressed this specific flaw in the locked_check_p function. Additionally, implementing network segmentation and access controls to limit exposure of the KDC service to untrusted networks can provide temporary protection while upgrades are pending. Security monitoring should be enhanced to detect unusual patterns of KDC daemon restarts or assertion failures that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to service stoppage and denial of service operations, making it particularly relevant for organizations implementing threat hunting and incident response procedures that focus on authentication infrastructure compromise.