CVE-2017-9287 in OpenLDAP
Summary
by MITRE
servers/slapd/back-mdb/search.c in OpenLDAP through 2.4.44 is prone to a double free vulnerability. A user with access to search the directory can crash slapd by issuing a search including the Paged Results control with a page size of 0.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-9287 represents a critical double free condition within the OpenLDAP implementation that affects versions through 2.4.44. This flaw exists in the servers/slapd/back-mdb/search.c file and specifically impacts the directory server's handling of paged results controls during search operations. The vulnerability stems from improper memory management practices where the same memory block gets freed twice under certain conditions, creating a potential for arbitrary code execution or service disruption. The issue is particularly concerning because it can be triggered by authenticated users who have search privileges within the directory service, making it exploitable in environments where directory access is granted to legitimate users.
The technical exploitation of this vulnerability occurs when a user performs a search operation that includes the Paged Results control with a page size parameter set to zero. This specific combination of parameters causes the memory management routines within the MDB (Memory-Mapped Database) backend to incorrectly handle memory deallocation, leading to the double free scenario. The flaw manifests during the search processing phase when the system attempts to free memory resources that have already been released, potentially allowing an attacker to manipulate the heap layout and execute malicious code. This type of vulnerability falls under CWE-415 which specifically addresses duplicate free conditions in memory management, and aligns with ATT&CK technique T1059.007 for execution through search operations.
The operational impact of CVE-2017-9287 extends beyond simple service disruption as it represents a potential path to privilege escalation or complete system compromise. When exploited successfully, the double free condition could allow an attacker to execute arbitrary code with the privileges of the slapd process, typically running with elevated permissions to access directory data. This creates a significant risk for organizations relying on OpenLDAP for authentication services, as directory servers often contain sensitive user credentials and access control information. The vulnerability is particularly dangerous in enterprise environments where directory services are critical infrastructure components, potentially enabling attackers to gain unauthorized access to sensitive data or disrupt authentication services for entire organizational domains.
Organizations should immediately implement mitigations including updating to OpenLDAP version 2.4.45 or later where the double free vulnerability has been resolved. The patch addresses the memory management issue by ensuring proper handling of memory deallocation when processing paged results controls with zero page sizes. Additionally, administrators should consider implementing access controls that limit directory search privileges to only necessary users and services, reducing the attack surface for this vulnerability. Network segmentation and monitoring should be implemented to detect unusual search patterns or attempts to trigger the vulnerability. The fix demonstrates the importance of proper memory management in server applications and highlights the need for thorough code review processes to identify similar issues in complex directory service implementations. Security teams should also consider implementing automated vulnerability scanning tools that can detect the presence of vulnerable OpenLDAP versions in their environments, as this vulnerability has been widely exploited in the wild and represents a common target for attackers seeking to compromise directory services.