Pierluigi Paganini August 17, 2019

Trend Micro addressed 2 DLL hijacking flaws in Trend Micro Password Manager that could allow malicious actors to escalate privileges and much more.

Security expert Peleg Hadar from SafeBreach discovered a DLL hijacking vulnerability in the Trend Micro Password Manager that could be exploited to execute arbitrary code with the permissions of the most privileged account on a Windows system.

The flaw, tracked as CVE-2019-14684, could allow an authenticated attacker to run with SYSTEM privileges an arbitrary, unsigned DLL file within a trusted process. 

“SafeBreach Labs discovered a new vulnerability in Trend Micro Password Manager software.” reads the post published by SafeBreach.

“In this post, we will demonstrate how this vulnerability could have been used in order to achieve privilege escalation and persistence by loading an arbitrary unsigned DLL into a service that runs as NT AUTHORITY\SYSTEM.”

The Trend Micro Password Manager is provided as a standalone application or integrated with Trend Micro Maximum Security product, it allows to manage website passwords and login IDs in one secure location.

The flaw resides in the “Trend Micro Password Manager Central Control Service” that fails to check if a certain DLL (tmtap.dll) is installed on the system.

According to the experts, the service executes the signed process PwmSvc.exe with SYSTEM privileges that then loads the Trend Micro Whitelist Module library (tmwlutil.dll), which attempts to load the tmtap.dll.

The tmtap.dll DLL is not loaded is a safe way from an absolute path, and the security software does not verify that the loaded DLL is signed.

The software searches the DLL also in system folders and also in c:/python27 that allowed exploitation.

“In our VM, the c:\python27 has an ACL which allows any authenticated user to write files onto the ACL. This makes the privilege escalation simple and allows a regular user to write the missing DLL file and achieve code execution as NT AUTHORITY\SYSTEM.” continues the advisory.

“It is important to note that an administrative user or process must (1) set the directory ACLs to allow access to non-admin user accounts, and (2) modify the system’s PATH variable to include that directory. This can be done by different applications.”

The expert wrote PoC exploit code for the privilege escalation, he compiled an unsigned DLL that wrote to a text file the name of the process loading it, the username that executed it, and the name of the DLL file.

The DLL ran with SYSTEM privileges within a signed Trend Micro process demonstrating the possible exploitation of the issue.

The expert explained that the exploit code will be executed every time the PwmSvc.exe service loads, allowing a malware using this mechanism to achieve persistence on a system running a vulnerable version of Trend Micro Password Manager.

Another researcher, Trần Văn Khang of Infiniti Team – VinCSS, reported a second DLL injection issue that was tracked as CVE-2019-14687.

This second vulnerability could be exploited using a different DLL.

“A separate, but similar DLL hijacking vulnerability exists in Trend Micro Password Manager 5.0, utilizing a separate DLL.” reads the security advisory published by Trend Micro.

Users having the automatic updates feature enabled in Trend Micro Password Manager should have already received the fix to address the flaws.

Trend Micro confirmed it is not aware of any actual attacks exploiting the above vulnerabilities.

Pierluigi Paganini

(SecurityAffairs – Trend Micro’s Password Manager, hacking)

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