VMware Host VMX Process Impersonation Hijack Privilege Escalation

The VMX process (vmware-vmx.exe) process configures and hosts an instance of VM. As is common with desktop virtualization platforms the VM host usually has privileged access into the OS such as mapping physical memory which represents a security risk. To mitigate this the VMX process is created with an elevated integrity level by the authentication daemon (vmware-authd.exe) which runs at SYSTEM. This prevents a non-administrator user opening the process and abusing its elevated access. Unfortunately the process is created as the desktop user and follows the common pattern of impersonating the user while calling CreateProcessAsUser. This is an issue as the user has the ability to replace any drive letter for themselves, which allows a non-admin user to hijack the path to the VMX executable, allowing the user to get arbitrary code running as a trusted VMX process. Affects VMware Workstation Windows version 14.1.5 (on Windows 10). Also tested on VMware Player version 15.0.2.

MD5 | c70a9a606361322046a94717d41168b1

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