TUCoPS :: Browsers :: bt353.txt

Internet Explorer Object Type Property Overflow

Internet Explorer Object Type Property Overflow

Release Date:
June 4, 2003

High (Remote Code Execution)

Systems Affected:
Microsoft Internet Explorer 5.01
Microsoft Internet Explorer 5.5
Microsoft Internet Explorer 6.0
Microsoft Internet Explorer 6.0 for Windows Server 2003

The "Object" tag is used to insert objects such as ActiveX components into
HTML pages. The "Type" property of the "Object" tag is used to set or
retrieve the MIME type of the object. Typical valid MIME types include
"plain/text" or "application/hta", "audio/x-mpeg", etc. A buffer overflow
has been discovered in the "Type" property of the "Object" tag. While there
is buffer checking in place, the buffer checking can be overcome by using a
special character. From there, the exploitation is a simple, stack-based
overflow that allows the remote attacker to run code of his/her choice on
the target system.

This attack may be utilized wherever IE parses HTML, so this vulnerability,
affects newsgroups, mailing lists, or websites.

Due to the popularity and prevalence of ActiveX on the Internet, users
running Windows 2003 "Enhanced Security Configuration" Mode may have chosen
to re-activate the ability to view active content for all websites instead
of continually adding websites to the "Internet" or "Trusted" zones on a
per-site basis.  These users should be aware that they are at risk for this
vulnerability and should apply the necessary patch.

Technical Description:
This example was designed for Windows 2000 with .Net Framework and the
latest IE.

<object type="[/x64]AAAAAAAAAAAAAAAA">Cooler Than Centra Spike</object>

Give or take a few '/' characters depending on the system. The issue is
relatively simple and interesting: the '/' character is changed into '_/_'
(three characters) after the string is checked for proper buffer size.
Because of this expansion, we are able to overrun the bounds of the buffer.
This allows us to take control of key registers so as to run code that we
specify, which will be available at the EDX register. At this point a JMP
EDX is called, and from there the payload can be executed.

This issue was discovered by using the same automated testing tool with
which we found the Shockwave, MSN Chat, and PNG issues. Additional time was
saved through "eVe", a proprietary vulnerability tracing tool which allows
for the viewing of checked and unchecked buffers as they are processed in

Retina® Network Security Scanner (http://www.eeye.com/Retina) has been
updated to identify this latest Internet Explorer vulnerability.

Vendor Status:
Microsoft was notified and has released a patch for this vulnerability. The
patch is available at:

Drew Copley, Research Engineer, eEye Digital Security

Thanks to Riley Hassell, Research Engineer -- for eVe, and various other
research help. Welcome to Unyun, of ShadowPenguin fame -- he swears there
are no ninjas left in Japan, but he is lying, and he is one. Also gr33t5
to... the Shadow, Wolverine, the Hulk, and the Punisher.

Copyright (c) 1998-2003 eEye Digital Security
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