:: Deepquest ::

A major component of Comodo Antivirus is the x86 emulator, which includes a number of shims for win32 API routines so that common API calls work in emulated programs (CreateFile, LoadLibrary, etc). The emulator itself is located in MACH32.DLL, which is compiled without /DYNAMICBASE, and runs as NT AUTHORITYSYSTEM. These API routines access memory from the emulated virtual machine, perform the requested operation, and then poke the result back into the emulator. Because these emulated routines are all native code, they must take care not to trust values extracted from the emulator, which is running attacker controlled code. Browsing through the list of emulated routines, MSVBVM60!rtcLowerCaseVar jumped out as an obvious case of integer overflow due to trusting attacker-provided parameters.