Various Lexmark Universal Printer drivers as listed at advisory TE953
allow low-privileged authenicated users to elevate their privileges to
SYSTEM on affected Windows systems by modifying the XML file at
C:\ProgramData\\Universal Color Laser.gdl
to replace the DLL path to unires.dll with a malicious DLL path.
When C:\Windows\System32\Printing_Admin_Scripts\en-US\prnmngr.vbs is
then used to add the printer to the affected system, PrintIsolationHost.exe,
a Windows process running as NT AUTHORITY\SYSTEM, will inspect the
C:\ProgramData\\Universal Color Laser.gdl file and will
load the malicious DLL from the path specified in the file. This which will
result in the malicious DLL executing as NT AUTHORITY\SYSTEM.
Once this module is finished, it will use the prnmngr.vbs script
to remove the printer it added.
- Jacob Baines
- Shelby Pace
- Grant Willcox