Panel::Software Customized WiX .be TEMP folder is vulnerable to DLL redirection attacks that allow the attacker to escalate privileges

Summary

# Summary

.be TEMP folder is vulnerable to DLL redirection attacks that allow the attacker to escalate privileges.

# Details

If the bundle is not run as admin, the user's TEMP folder is used and not the system TEMP folder. A utility is able to monitor the user's TEMP folder for changes and drop its own DLL into the .be/.Local folder immediately when the .be folder is created. When the burn engine elevates, the malicious DLL receives elevated privileges.

# PoC

As a standard, non-admin user:

1. Monitor the user's TEMP folder for changes using ReadDirectoryChangesW 1. On FILE_ACTION_ADDED, check if the folder name is .be 1. Create a folder in .be named after the bundle + .Local (e.g. MyInstaller.exe.Local) 1. Put the malicious COMCTL32.DLL in the .Local folder following the naming used for the real DLL (e.g. MyInstaller.exe.Local/x86_microsoft.windows.common-controls_.../COMCTL32.dll) 1. Do hacker things when the engine escalates and the malicious DLL is loaded

Proper naming for the path can be obtained by using GetModuleHandle("comctl32.dll") and GetModuleFileName.

# Impact

DLL redirection utilizing .exe.Local Windows capability. This impacts any installer built with the WiX installer framework.