CVE-2012-1849 in Lync
Summary
by MITRE
Untrusted search path vulnerability in Microsoft Lync 2010, 2010 Attendee, and 2010 Attendant allows local users to gain privileges via a Trojan horse DLL in the current working directory, as demonstrated by a directory that contains a .ocsmeet file, aka "Lync Insecure Library Loading Vulnerability."
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Analysis
by VulDB Data Team • 06/09/2021
The CVE-2012-1849 vulnerability represents a critical untrusted search path weakness affecting Microsoft Lync 2010 client applications including the standard Lync 2010, Lync 2010 Attendee, and Lync 2010 Attendant versions. This vulnerability falls under the CWE-427 category of Untrusted Search Path, which specifically addresses the dangerous practice of loading dynamic link libraries from directories that are not properly secured or validated. The flaw manifests when the Lync client applications fail to properly validate the source of dynamic libraries and instead rely on the standard Windows library search order, which includes the current working directory as a potential location for DLL resolution. This behavior creates a dangerous privilege escalation vector where a local attacker can place a malicious Trojan horse DLL in the same directory as a legitimate Lync executable or configuration file, specifically targeting the .ocsmeet file extension which is used by Lync for meeting invitations and configurations.
The technical exploitation of this vulnerability occurs through a carefully crafted directory structure that contains both a legitimate .ocsmeet file and a malicious DLL with the same base name as the expected library. When the Lync application processes the .ocsmeet file, it attempts to load a required dynamic library from the current working directory without proper validation of the library's source or integrity. This allows the attacker to place a malicious DLL in the working directory that will be loaded instead of the legitimate system library, enabling arbitrary code execution with the privileges of the user running the Lync client. The vulnerability is particularly concerning because it leverages the Windows DLL search order mechanism, which is a well-known security weakness that has been documented in multiple security frameworks including the ATT&CK framework under the T1059.001 technique for execution through command and scripting interpreter. The attack requires local system access and minimal privileges to execute, making it a particularly attractive vector for privilege escalation attacks within corporate environments where Lync is commonly deployed.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable full system compromise within organizations that rely heavily on Microsoft Lync for communication. Attackers can leverage this vulnerability to establish persistent backdoors, exfiltrate sensitive meeting data, or use the compromised Lync client as a launching point for further attacks against other network resources. The vulnerability affects organizations that have deployed Lync 2010 across their enterprise infrastructure, particularly those with less stringent security controls around user directories and file system permissions. Organizations using Lync 2010 in environments with multiple users sharing common directories or where users may have access to modify working directories can be particularly vulnerable. The attack surface is broad since Lync clients are commonly run by users with varying privilege levels, and the vulnerability can be exploited through social engineering techniques where users are tricked into opening malicious .ocsmeet files in directories containing the attacker-controlled DLLs. This vulnerability aligns with the ATT&CK framework's T1068 technique for escalation of privileges through local exploitation and represents a classic example of how insecure library loading practices can create persistent security weaknesses in enterprise communication platforms.
Mitigation strategies for CVE-2012-1849 should focus on both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities in the future. The most effective immediate solution is to apply the official Microsoft security updates that address this specific vulnerability by implementing proper DLL loading mechanisms that do not rely on the insecure Windows search order. Organizations should also implement strict directory permissions and file system controls to prevent users from placing executable files in locations where Lync applications might be executed. Security awareness training for users to recognize potentially malicious .ocsmeet files and other file types that could be used in such attacks is essential. Network segmentation and the principle of least privilege should be enforced to limit the potential impact of successful exploitation. Additionally, organizations should consider implementing application whitelisting solutions that prevent unauthorized DLLs from executing in the context of legitimate Lync processes. The vulnerability highlights the importance of following secure coding practices as outlined in Microsoft's Secure Coding Guidelines and the OWASP Secure Coding Practices, particularly regarding proper library loading and path validation. Regular security assessments and vulnerability scanning should include checks for similar insecure library loading patterns in other enterprise applications to prevent analogous vulnerabilities from being exploited in the future.