Windows: Dolby Audio X2 Service Elevation of Privilege
Platform: Windows 10 + Realtek Audio Driver version 6.0.1.7898 (on a Lenovo P50). Version of the service binary 0.7.2.61 built on 7/18/2016.
Class: Elevation of Privilege

Summary:
The DAX2API service installed as part of the Realtek Audio Driver on Windows 10 is vulnerable to a privilege escalation vulnerability which allows a normal user to get arbitrary system privileges.

Description:

The DAX2API service is a DCOM service written in .NET running at system privileges. The use of .NET for DCOM is inherently unsafe and should not be used. There’s public exploit code to elevate privileges on arbitrary services available at https://github.com/tyranid/ExploitDotNetDCOM.

Microsoft recommends moving from using DCOM to WCF for .NET services of different privilege levels. See https://blogs.technet.microsoft.com/srd/2014/10/14/more-details-about-cve-2014-4073-elevation-of-privilege-vulnerability/ for more information.

Proof of Concept:

To demonstrate the vulnerability download the project https://github.com/tyranid/ExploitDotNetDCOM and compile using Visual Studio. The executable to use is ExploitDotNetDCOMSerialization.exe.

1) From a command prompt run the command “ExploitDotNetDCOMSerialization.exe 6A28A945-790C-4B68-B0F4-34EEB1626EE3 notepad” 
2) Check the currently running processes for the privileged copy of notepad,

Expected Result:
No privilege escalation occurs.

Observed Result:
An instance of notepad is running at system privileges.

This bug is subject to a 90 day disclosure deadline. If 90 days elapse without a broadly available patch, then the bug report will automatically become visible to the public.