A vulnerability in McAfee antivirus software could allow an attacker to evade self-defense mechanisms and achieve persistence, SafeBreach security researchers have discovered.
The security flaw could be abused to load unsigned DLLs into multiple services that run as NT AUTHORITYSYSTEM. The exploitation, however, requires for the attacker to have admin privileges.
Multiple parts of the antivirus solutions run as a Windows service executed as “NT AUTHORITYSYSTEM,” which means they have powerful permissions on the system, SafeBreach explains.
The affected processes, the security researchers discovered, attempt to load a file from the path C:WindowsSystem32wbemwbemcomn.dll. However, because the DLL is located in the System32 folder, it cannot be found.
This mechanism, however, could be exploited by an attacker to load a malicious DLL by placing their file in the wbem folder, under the name wbemcomn.dll.
Having an unsigned library loaded by the McAfee software process would result in bypassing the self-defense mechanism of the antivirus, which prevents users, and even administrators, from writing to its folders.
Another issue that makes the bypass possible is that the antivirus performs no digital signature validation against the DLL file.
“The vulnerability gives attackers the ability to load and execute malicious payloads in a persistent way, each time the services are loaded. That means that once the attacker drops a malicious DLL, the services will load the malicious code each time the services are restarted,” SafeBreach explains.
Tracked as CVE-2019-3648, the vulnerability impacts McAfee Total Protection (MTP), McAfee Anti-Virus Plus (AVP), and McAfee Internet Security (MIS).
McAfee, which learned of the security bug in August, has already issued a patch and says it is not aware of the vulnerability being exploited in attacks.
“Prior to this update MTP, AVP, and MIS were not checking that these third-party files had the correct digital signatures and were loaded from the correct location. This could allow an attacker with administrative permissions to the computer to place their malicious programs in specific locations and the MTP, AVP, and MIS programs would load and run them,” McAfee notes in an advisory.
A couple of weeks ago, SafeBreach revealed that antivirus products from Avast, AVG, and Avira were also impacted by DLL hijacking vulnerabilities exploitable in a similar manner by attackers with administrative privileges.