VMware: Host VMX Process Impersonation Hijack EoP
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. While having an elevated integrity level isn’t especially dangerous, the fact that arbitrary code is running as a “trusted” VMX process means you can access all the facilities for setting up VMs, such as the “opensecurable” command which allows the process to open almost any file as SYSTEM for arbitrary read/write access which could easily be used to get administrator privileges. Write file write access you could perform an attack similar to https://googleprojectzero.blogspot.com/2018/04/windows-exploitation-tricks-exploiting.html.
