CVE-2012-0833 in 389 Directory Server
Summary
by MITRE
The acllas__handle_group_entry function in servers/plugins/acl/acllas.c in 389 Directory Server before 1.2.10 does not properly handled access control instructions (ACIs) that use certificate groups, which allows remote authenticated LDAP users with a certificate group to cause a denial of service (infinite loop and CPU consumption) by binding to the server.
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Analysis
by VulDB Data Team • 01/03/2025
The vulnerability described in CVE-2012-0833 represents a critical flaw in the 389 Directory Server authentication and access control mechanisms. This issue specifically affects the acllas__handle_group_entry function within the server's access control list implementation, where improper handling of certificate-based group memberships creates a significant security risk. The vulnerability exists in versions prior to 1.2.10 of the 389 Directory Server, which is a widely used open source directory server implementation that serves as a foundation for enterprise identity management systems.
The technical flaw manifests when LDAP users authenticated through certificate groups attempt to bind to the server with malformed or specially crafted access control instructions. The acllas__handle_group_entry function fails to properly validate or process these certificate group references, leading to an infinite loop condition in the server's processing logic. This flaw specifically impacts how the server handles ACI (Access Control Instruction) entries that reference certificate groups, causing the server to enter a continuous processing cycle that consumes excessive CPU resources. The vulnerability is particularly dangerous because it requires only authenticated access through LDAP binding, making it exploitable by users who have already established legitimate credentials within the directory service.
The operational impact of this vulnerability is severe, as it enables a denial of service attack that can completely incapacitate the directory server. An attacker with valid certificate-based authentication credentials can trigger the infinite loop condition, causing the server to consume 100% CPU resources and effectively rendering the directory service unavailable to legitimate users. This creates a cascading effect throughout the enterprise environment that relies on the directory server for authentication, authorization, and identity management services. The attack is particularly insidious because it can be executed by authenticated users who may have legitimate access rights, making it difficult to detect and mitigate without proper monitoring and access controls in place. This vulnerability directly maps to CWE-835, which describes the weakness of infinite loops or recursive calls without proper termination conditions.
The exploitability of this vulnerability aligns with several ATT&CK techniques including privilege escalation and denial of service operations. Attackers can leverage their existing authenticated access to perform resource exhaustion attacks that compromise the availability of critical directory services. The vulnerability demonstrates the importance of proper input validation and boundary checking in access control implementations, as the lack of proper validation allows malformed certificate group references to cause system instability. Organizations using 389 Directory Server should implement immediate mitigations including upgrading to version 1.2.10 or later, which contains the necessary fixes for proper ACI handling. Additionally, monitoring for unusual CPU consumption patterns and implementing rate limiting for LDAP bind operations can help detect and prevent exploitation attempts.
Security practitioners should recognize that this vulnerability represents a fundamental flaw in how certificate-based access control groups are processed within directory services, highlighting the need for comprehensive testing of access control logic during security assessments. The fix implemented in version 1.2.10 addresses the root cause by ensuring proper validation of certificate group references and implementing appropriate loop detection mechanisms. Organizations should also consider implementing additional security controls such as LDAP query monitoring, access logging, and automated alerting for unusual resource consumption patterns. This vulnerability serves as a reminder of the critical importance of proper access control implementation in enterprise directory services and the potential for seemingly minor flaws to create significant operational impacts. The remediation process should include thorough testing to ensure that the patch does not introduce regressions in legitimate access control functionality while effectively preventing the denial of service condition.