Microsoft Internet Explorer DoS in Rendering Malicious PNG Files.

*Version Affected:*
IE 7 / IE 8 BETA

*Severity:*
Intermediate

*Background:*
Mshtml.dll is a standard library which is responsible for rendering
objects in web pages in Internet Explorer.

*Description:*
The Internet Explorer 7 is vulnerable to Denial of Service while 
handling malicious
PNG files. The IE shows a intrinsic vulnerable response while loading 
images.This
issue can be exploited by an attacker by letting a victim to visit a 
malicious web page
embedded with rogue PNG Files there by leading to denial of service.

*Analysis:*
The internet explorer unable to render and load the malicious png 
image.On further discussion ,
Microsoft team stated that CDwnTaskExec::ThreadExec enters an infinite 
loop that that keeps
grabbing task and runs them synchronously.This results in failure in 
completion of task.When a
 task never completes,or timeouts all subsequent task will be blocked. 
IE will fail to load all
subsequent image after an attempt to load the malicious PNG file.

*Detection:*
SecNiche confirmed this vulnerability affects Internet Explorer 7 and 
Internet Explorer 8 Beta
on the Microsoft Windows XP SP2 platform.The versions tested are:

7.0.5730
8.0.6001

*Links:
http://www.secniche.org/ie_mal_png_dos.html 
*
*Disclosure Timeline:*
April 6,2008 Initial Vendor Notification
April 7,2008 Initial Vendor Response
September 17 ,2008 Release Date.

*Vendor Response:*
Microsoft Acknowledges this vulnerability and "fix" will be
released in the final version of Internet Explorer 8 later this year.

*Credit:*
Aditya K Sood

*Disclaimer*
The information in the advisory is believed to be accurate at the time 
of publishing
based on currently available information. Use of the information 
constitutes acceptance
 for use in an AS IS condition. There is no representation or 
warranties, either express or
implied by or with respect to anything in this document, and shall not 
be liable for any
 implied warranties of merchantability or fitness for a particular 
purpose or for any indirect
special or consequential damages.