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Re: Microsoft Internet Explorer Local File Accesses Vulnerability

From: "pdp (architect)" <pdp.gnucitizen () googlemail com>
Date: Tue, 20 Feb 2007 09:57:30 +0000
hi Rajesh,

Maybe it is too early in the morning in UK and that's why I may act
like a stupid, but how come this is a vulnerability? For sure you can
open files from the file system by using various HTML elements but can
you really read their content, I don't think so.

Firefox has done a good job in restricting access to local files if
they are called from remote locations such as http and https. This
rule, however, can be circumvented in a number of ways. IE does
perform some of these checks, although, I have tested the POC you
provided and I cannot see it working. I am running XP SP2, no lock
downs what so ever.

I see how this trick can be used to identify the operating system
version but again, this is not a new thing. You can do similar stuff
with the res:// protocol. In fact you can use this protocol to
identify currently installed applications, which I believe is pretty
cool.

So, can you explain why this is a hole and how it can be used by attackers? :)

Thanks man,
All the best

On 2/19/07, Rajesh Sethumadhavan <rajesh.sethumadhavan () yahoo com> wrote:



Microsoft Internet Explorer Local File Accesses Vulnerability

#####################################################################
XDisclose Advisory        : XD100099
Vulnerability Discovered : February 10th 07
Advisory Released         : February 20th 07
Credit                           : Rajesh Sethumadhavan

Class                           : Local File Accesses
Severity                        : Critical
Solution Status             : Unpatched
Vendor                         : Microsoft Corporation
Affected applications     : Microsoft Internet Explorer
Affected version            : Microsoft Internet Explorer 6 confirmed
                                    (Other versions may be
also affected)
Affected Platform          : Windows XP Professional SP0,SP1,SP2
                                      Windows Home Edition
SP0,SP1,SP2
                                     Windows 2003

#####################################################################


Overview:
Microsoft Internet Explorer is a default browser bundled with all
versions of Microsoft Windows operating system.

Description:
A vulnerability has been identified in Microsoft Internet Explorer,
(default installation) in windows XP service pack 2 which could be
exploited by malicious users to obtain victims local files. This flaw
is due to an error in the way Microsoft Internet explorer handles
different html tags. Which could be exploited by a malicious remote
user to obtain sensitive local files from the victim's computer.
Vulnerability Insight :
Microsoft Windows explorer is not handling various html tags like "img"
"script" "embed" "object" "param" "style" "bgsound" "body" "input"
(Other tags may be also vulnerable). By using the file protocol along
with above tags it is possible to accesses victims local files.

a) Embed Tag Local file Accesses:
---------------------------------------------------------------------
<EMBED SRC="file:///C:/test.pdf" HEIGHT=600 WIDTH=1440></EMBED>
---------------------------------------------------------------------

b) Object & Param Tag Local File Accesses:
---------------------------------------------------------------------
<object type="audio/x-mid" data=" file:///C:/test.mid" width="200"
height="20">
  <param name="src" value="file:///C:/test.mid">
  <param name="autoStart" value="true">
  <param name="autoStart" value="0">
</object>
---------------------------------------------------------------------

c) Body Tag Local File Accesses:
---------------------------------------------------------------------
<body background="file:///C:/test.gif" onload="alert('loading body
bgrd success')" onerror="alert('loading body bgrd error')">
---------------------------------------------------------------------

d) Style Tag Local File Accesses:
---------------------------------------------------------------------
<STYLE type="text/css">BODY{background:url("
file:///C:/test.gif")}
</STYLE>
---------------------------------------------------------------------

e) Bgsound Tag Local File Accesses:
---------------------------------------------------------------------
<bgsound src="file:///C:/test.mid" id="soundeffect" loop=1 autostart=
"true"/>
---------------------------------------------------------------------

f) Input Tag Local File Accesses:
---------------------------------------------------------------------
<form>
  <input type="image" src=" file:///C:/test.gif" onload="alert('loading
  input success')" onerror="alert('loading input error')">
</form>
---------------------------------------------------------------------

g) Image Tag Local File Accesses:
---------------------------------------------------------------------
<img src="file:///C:/test.jpg" onload="alert('loading image success')"
onerror="alert('loading image error')">
---------------------------------------------------------------------

h) Script Tag Local File Accesses:
---------------------------------------------------------------------
<script src="file:///C:/test.js"></script >
---------------------------------------------------------------------


Exploitation method:
- Creates a web page or an HTML Mail with the vulnerable code
- When the victim opens the mail or visit the vulnerable site it is
  possible to accesses his local files.

Demonstration:
Note: Demonstration will try to accesses few default images and wave
files

- Visit the POC
- If vulnerable internet explorer is used it will show your local
  sample images and give a proper alert.

Solution:
No solution

Screenshot:
http://www.xdisclose.com/images/xdiscloselocalie.jpg

Proof Of Concept:
http://www.xdisclose.com/poc/xdiscloselocalie.html

Impact:
A Remote user can get accesses to victims local system files.

Scope of impact is limited to system level.

Original Advisory:
http://www.xdisclose.com/XD100099.txt

Credits:
Rajesh Sethumadhavan has been credited with the discovery of this
vulnerability

Disclaimer:
This entire document is strictly for educational, testing and
demonstrating purpose only. Modification use and/or publishing this
information is entirely on your own risk. The exploit code is to be
used on your testing environment only. I am not liable for any direct
or indirect damages caused as a result of using the information or
demonstrations provided in any part of this advisory.


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-- 
pdp (architect) | petko d. petkov
http://www.gnucitizen.org

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