CVE-2007-5708 in OpenLDAP
Summary
by MITRE
slapo-pcache (overlays/pcache.c) in slapd in OpenLDAP before 2.3.39, when running as a proxy-caching server, allocates memory using a malloc variant instead of calloc, which prevents an array from being initialized properly and might allow attackers to cause a denial of service (segmentation fault) via unknown vectors that prevent the array from being null terminated.
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Analysis
by VulDB Data Team • 07/29/2019
The vulnerability identified as CVE-2007-5708 resides within the slapo-pcache overlay component of OpenLDAP's slapd daemon, specifically in the file overlays/pcache.c. This flaw manifests when the server operates in proxy-caching mode, a configuration where OpenLDAP functions as an intermediary between clients and backend directory servers while caching results to improve performance. The vulnerability stems from improper memory allocation practices that create conditions conducive to system instability and potential denial of service scenarios.
The technical root cause involves the use of malloc instead of calloc for memory allocation within the pcache overlay implementation. While malloc allocates memory without initializing its contents, calloc performs both allocation and zero-initialization of the allocated memory block. This distinction becomes critical when dealing with arrays that require proper initialization to function correctly. The improper allocation method prevents an array from being properly initialized, leading to unpredictable memory states that can result in segmentation faults during normal operation.
When the pcache overlay processes requests in proxy-caching mode, it relies on properly initialized arrays to manage cached data structures and maintain consistency between the cache and the backend servers. The failure to initialize these arrays correctly means that array elements may contain garbage values or undefined data, which can cause the application to behave unpredictably. The vulnerability specifically mentions that the array may not be null terminated, a condition that can lead to memory access violations when the application attempts to traverse or process the array elements.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially compromise the stability and reliability of the entire directory service infrastructure. In proxy-caching scenarios, where OpenLDAP serves as a critical middleware component, a segmentation fault can cause the slapd process to terminate abruptly, disrupting directory services for all connected clients. This disruption can cascade through applications and services that depend on LDAP authentication and directory lookups, creating widespread service degradation.
This vulnerability aligns with CWE-457, which describes the use of uninitialized variables, and demonstrates how improper memory management can lead to system instability. From an ATT&CK perspective, this represents a denial of service attack vector that could be exploited by adversaries seeking to disrupt directory services, potentially impacting authentication systems that rely on LDAP infrastructure. The attack surface is particularly concerning in enterprise environments where LDAP servers serve as foundational components for identity management and access control.
The recommended mitigation strategy involves upgrading to OpenLDAP version 2.3.39 or later, where the memory allocation issue has been corrected to use calloc instead of malloc for the affected array initialization. System administrators should also implement monitoring to detect abnormal process termination patterns that might indicate exploitation attempts. Additionally, organizations should consider implementing proper input validation and bounds checking mechanisms to further harden their LDAP infrastructure against similar memory-related vulnerabilities. The fix addresses the core memory management issue by ensuring proper initialization of array elements, thereby preventing the segmentation fault conditions that could be triggered by malformed or unexpected input data processed through the proxy-caching overlay.