CVE-2011-1529 in Kerberos
Summary
by MITRE
The lookup_lockout_policy 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 db2 (aka Berkeley DB) or LDAP back end is used, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via vectors that trigger certain process_as_req errors.
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Analysis
by VulDB Data Team • 08/04/2024
The vulnerability identified as CVE-2011-1529 represents a critical denial of service flaw within the Key Distribution Center component of MIT Kerberos 5 implementations. This weakness specifically affects versions ranging from 1.8 through 1.8.4 and 1.9 through 1.9.1 when utilizing either the Berkeley DB or LDAP backend storage mechanisms. The vulnerability stems from inadequate error handling within the lookup_lockout_policy function, which is responsible for managing account lockout policies in authentication scenarios. When certain process_as_req errors occur during Kerberos authentication requests, the function fails to properly validate pointer references, leading to a NULL pointer dereference condition that ultimately causes the KDC daemon to crash and terminate operations.
The technical exploitation of this vulnerability occurs through carefully crafted authentication requests that trigger specific error conditions within the KDC's processing pipeline. When the lookup_lockout_policy function attempts to access memory locations that have not been properly initialized or have been set to NULL, the system experiences a segmentation fault or access violation that results in daemon termination. This behavior aligns with CWE-476, which describes NULL pointer dereference vulnerabilities, and demonstrates how improper validation of authentication state can lead to service disruption. The attack vector specifically targets the authentication backend processing, making it particularly dangerous in environments where Kerberos is critical for network authentication and access control.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise network availability and authentication infrastructure. Organizations relying on Kerberos for single sign-on capabilities, secure remote access, and network service authentication face significant risks when this vulnerability is exploited. The daemon crash creates a window of unavailability that can persist until manual intervention or automatic restart mechanisms are triggered, potentially affecting thousands of users and services dependent on the compromised Kerberos infrastructure. This vulnerability directly maps to ATT&CK technique T1499.004, which covers network disruption through denial of service attacks, and represents a critical weakness in the authentication infrastructure that could be leveraged by attackers to create persistent service availability issues.
Mitigation strategies for CVE-2011-1529 should focus on immediate patch deployment for affected Kerberos versions, with particular attention to systems using the db2 or LDAP backends. Organizations should implement monitoring solutions to detect unusual daemon crash patterns or authentication request anomalies that might indicate exploitation attempts. Network segmentation and access controls should be strengthened around Kerberos servers to limit exposure to potential attackers. The fix implemented by MIT Kerberos developers involved adding proper NULL pointer validation within the lookup_lockout_policy function to prevent the daemon from crashing when encountering malformed authentication requests. Additionally, system administrators should consider implementing automated restart mechanisms for KDC services and establishing robust logging procedures to track authentication failures that might precede exploitation attempts.