CVE-2017-2591 in 389 Directory Server
Summary
by MITRE
389-ds-base before version 1.3.6 is vulnerable to an improperly NULL terminated array in the uniqueness_entry_to_config() function in the "attribute uniqueness" plugin of 389 Directory Server. An authenticated, or possibly unauthenticated, attacker could use this flaw to force an out-of-bound heap memory read, possibly triggering a crash of the LDAP service.
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Analysis
by VulDB Data Team • 03/08/2023
The vulnerability identified as CVE-2017-2591 affects the 389 Directory Server software family, specifically targeting the attribute uniqueness plugin within the 389-ds-base component. This issue resides in the uniqueness_entry_to_config() function where a critical flaw exists in memory handling that can lead to significant security implications. The 389 Directory Server represents a comprehensive enterprise-grade directory service implementation that provides LDAP (Lightweight Directory Access Protocol) functionality for managing directory information across large-scale networks. The attribute uniqueness plugin serves as a critical component for maintaining data integrity by ensuring that specific attributes within directory entries remain unique across the directory structure, making this vulnerability particularly concerning for systems relying on consistent directory data management.
The technical flaw manifests as an improperly null-terminated array within the uniqueness_entry_to_config() function, which operates as part of the directory server's configuration processing pipeline. This memory management error occurs when the plugin processes directory entries that contain attribute uniqueness configurations, specifically during the conversion of entry data into internal configuration structures. The improper null termination creates a condition where heap memory reads extend beyond the boundaries of allocated memory regions, potentially allowing an attacker to access uninitialized memory locations or memory that has been deallocated. This type of vulnerability falls under the CWE-121 category of "Stack-based Buffer Overflow" and can be classified as a heap-based memory corruption issue that directly relates to improper memory handling practices. The vulnerability represents a classic example of how insufficient input validation and memory boundary checking can create exploitable conditions in server-side applications.
The operational impact of this vulnerability extends beyond simple service disruption, as it creates potential for more severe security consequences depending on the attack vector and system configuration. While the vulnerability description indicates that authentication may not be required for exploitation, the nature of the flaw suggests that it could be leveraged by attackers to cause denial of service through service crashes or potentially escalate privileges if the LDAP service operates with elevated privileges. The heap memory read operations could expose sensitive information from memory locations that should remain protected, though the primary risk manifests as service availability disruption. The vulnerability affects systems where the attribute uniqueness plugin is enabled and actively processing directory entries, which represents a significant portion of 389 Directory Server installations in enterprise environments where data integrity and consistency are paramount. Organizations running these directory services face potential disruption of directory-based authentication, authorization, and service discovery mechanisms that rely on the stability of the LDAP infrastructure.
Mitigation strategies for CVE-2017-2591 focus primarily on upgrading to patched versions of the 389 Directory Server software, specifically versions 1.3.6 and later where the memory handling issue has been resolved. System administrators should conduct immediate vulnerability assessments to identify affected systems and prioritize patch deployment across all directory server instances. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service and represents a potential pathway for privilege escalation if exploited in systems where the LDAP service operates with administrative privileges. Additional defensive measures include implementing network segmentation to limit access to directory services, enabling monitoring for unusual LDAP service behavior, and conducting regular security audits of directory configurations. Organizations should also consider implementing intrusion detection systems that can identify abnormal memory access patterns or service disruptions that might indicate exploitation attempts. The fix implemented in version 1.3.6 addresses the root cause by ensuring proper null termination of arrays during the configuration processing, thereby preventing the out-of-bounds memory read conditions that enabled the vulnerability. This remediation approach aligns with standard secure coding practices that emphasize proper memory management and input validation as fundamental security controls for preventing memory corruption vulnerabilities.