CVE-2015-1546 in MacOS X
Summary
by MITRE
Double free vulnerability in the get_vrFilter function in servers/slapd/filter.c in OpenLDAP 2.4.40 allows remote attackers to cause a denial of service (crash) via a crafted search query with a matched values control.
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Analysis
by VulDB Data Team • 09/22/2022
The CVE-2015-1546 vulnerability represents a critical double free error within the OpenLDAP implementation that affects version 2.4.40 and potentially earlier releases. This flaw exists within the get_vrFilter function located in the servers/slapd/filter.c source file, making it a core component of the directory service's filtering mechanism. The vulnerability specifically manifests when processing crafted search queries that include matched values control, exposing a fundamental memory management issue that can be exploited remotely.
The technical nature of this vulnerability stems from improper memory handling within the filter processing code where the same memory block gets freed twice during the execution of the get_vrFilter function. This double free condition occurs when the software processes a specially crafted search query containing matched values control, leading to unpredictable memory state corruption. The flaw operates at the application layer and requires no authentication to exploit, making it particularly dangerous in networked environments where OpenLDAP servers are accessible to unauthenticated users. The vulnerability is classified under CWE-415 as an improper double free condition, which directly relates to memory safety issues in software implementations.
From an operational impact perspective, this vulnerability enables remote attackers to execute a denial of service attack against OpenLDAP servers, causing them to crash and become unavailable to legitimate users. The crash occurs when the malicious search query triggers the double free condition, leading to a segmentation fault or similar memory corruption error that terminates the slapd process. This disruption can severely impact directory services that rely on OpenLDAP for user authentication, authorization, and information management, potentially affecting thousands of users and applications dependent on the directory service. The attack vector is particularly concerning because it can be executed over the network without requiring any privileged access or credentials, making it a preferred target for attackers seeking to disrupt services.
Organizations should implement immediate mitigations including applying the vendor-provided patches released for OpenLDAP version 2.4.41 and later, which address the double free condition in the get_vrFilter function. Network administrators should also consider implementing access controls to limit exposure of OpenLDAP servers to untrusted networks and monitor for suspicious search queries that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management in server applications and aligns with ATT&CK technique T1499.004 for network denial of service attacks. Additionally, regular security assessments and code reviews focusing on memory handling patterns should be conducted to identify similar issues in other software components, as this type of vulnerability often indicates broader security weaknesses in application development practices.