CVE-2020-7312 in McAfee
Summary
by MITRE
DLL Search Order Hijacking Vulnerability in the installer in McAfee Agent (MA) for Windows prior to 5.6.6 allows local users to execute arbitrary code and escalate privileges via execution from a compromised folder.
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Analysis
by VulDB Data Team • 09/11/2020
This vulnerability represents a critical privilege escalation flaw in McAfee Agent installer components affecting versions prior to 5.6.6 on Windows systems. The issue stems from improper DLL search order handling during the installation process, creating a window where malicious actors can inject arbitrary code into the system. The vulnerability specifically targets the installer's execution path where it searches for required dynamic link libraries, allowing local users to place malicious DLLs in directories that are searched before legitimate system locations. This behavior aligns with CWE-427, which describes uncontrolled search path used in a web application, and more specifically CWE-157, which addresses improper handling of search paths. The flaw enables attackers to execute code with elevated privileges, potentially leading to complete system compromise. When a compromised folder is placed in the search path before the legitimate system directories, the installer loads malicious DLLs instead of the intended legitimate ones, creating a persistent backdoor mechanism. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1068, which covers privilege escalation through exploitation of software vulnerabilities, and T1574, which covers hijacking execution flow through dynamic link library injection.
The technical implementation of this vulnerability exploits the Windows DLL search order mechanism where the system first searches the application directory, then the system directory, followed by the Windows directory, and finally the directories listed in the PATH environment variable. In the McAfee Agent installer context, if a local attacker can control or manipulate the search path, they can place a malicious DLL with the same name as a legitimate dependency. This allows the installer to load the malicious code instead of the intended legitimate DLL, executing arbitrary code with the privileges of the installer process. The vulnerability is particularly dangerous because the installer typically runs with elevated privileges, making the privilege escalation aspect of this flaw extremely significant. Attackers can leverage this to gain SYSTEM level access to target systems, which would otherwise require more complex exploitation techniques. The impact extends beyond simple code execution to include potential data exfiltration, system persistence mechanisms, and further lateral movement within compromised networks.
Mitigation strategies for this vulnerability should focus on immediate patching of McAfee Agent installations to version 5.6.6 or later, which contains the necessary fixes for the DLL search order handling. Organizations should also implement strict directory permissions and access controls to prevent local users from placing files in critical system directories. Network segmentation and privilege separation can help limit the potential impact of successful exploitation attempts. Security monitoring should include detection of unusual DLL loading patterns and suspicious installer activities. The fix implemented by McAfee addresses the core search order issue by ensuring that legitimate system directories are prioritized over user-controlled locations during the DLL resolution process. Additionally, system administrators should conduct thorough vulnerability assessments to identify any other applications or processes that may exhibit similar search order vulnerabilities. Regular security audits of installation processes and privilege escalation mechanisms should be performed to prevent similar issues from emerging in other security software components. The vulnerability demonstrates the critical importance of proper DLL search order implementation in security software and highlights the need for robust privilege management in installation processes. Organizations should also consider implementing application whitelisting solutions to prevent unauthorized DLL loading and execution, which would provide additional defense in depth against similar exploitation techniques.