CVE-2011-1527 in Kerberos
Summary
by MITRE
The kdb_ldap plugin in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.9 through 1.9.1, when the LDAP back end is used, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a kinit operation with incorrect string case for the realm, related to the is_principal_in_realm, krb5_set_error_message, krb5_ldap_get_principal, and process_as_req functions.
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Analysis
by VulDB Data Team • 08/04/2024
The vulnerability CVE-2011-1527 represents a critical denial of service flaw within the Key Distribution Center of MIT Kerberos 5 versions 1.9 through 1.9.1 when utilizing the LDAP backend functionality. This issue specifically affects the kdb_ldap plugin which handles principal and realm management through Lightweight Directory Access Protocol integration. The vulnerability stems from insufficient input validation and error handling within the Kerberos authentication process, creating a scenario where malformed realm names can trigger catastrophic system failures.
The technical exploitation occurs through a carefully crafted kinit operation that submits realm names with incorrect string casing, specifically targeting the is_principal_in_realm function which fails to properly validate incoming realm parameters. When this function encounters improperly formatted realm strings, it triggers a NULL pointer dereference in the krb5_set_error_message function, subsequently propagating through the krb5_ldap_get_principal and process_as_req functions. This cascade of failures results in the KDC daemon crashing and restarting, effectively rendering the authentication service unavailable to legitimate users. The vulnerability directly maps to CWE-476 which describes NULL pointer dereference conditions, and represents a classic example of improper error handling in security-critical components.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a reliable method to compromise Kerberos infrastructure availability. Organizations relying on Kerberos for network authentication, particularly those utilizing LDAP-backed KDC implementations, face significant risk from this flaw. The attack requires minimal privileges and can be executed remotely, making it particularly dangerous in enterprise environments where Kerberos serves as the foundation for single sign-on and secure authentication services. System administrators may experience frequent service interruptions and potential credential caching issues that could compound the impact of the denial of service attack.
Mitigation strategies for CVE-2011-1527 should prioritize immediate patching of affected MIT Kerberos installations to versions 1.9.2 or later where the vulnerability has been addressed through improved input validation and error handling mechanisms. Organizations should implement monitoring solutions to detect unusual kinit operations that might indicate exploitation attempts, particularly those involving realm names with inconsistent casing patterns. Network segmentation and access controls should be strengthened around KDC services to limit potential attack vectors, while regular security assessments should verify proper implementation of Kerberos configurations. Additionally, system administrators should establish robust incident response procedures specifically for Kerberos-related service disruptions, ensuring rapid recovery and forensic analysis capabilities to prevent prolonged service outages that could impact enterprise security posture and user productivity.