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Microsoft XML Core Services XMLDOM Memory Corruption Vulnerability



iDefense Security Advisory 08.14.07: Microsoft XML Core Services XMLDOM Memory Corruption Vulnerability
iDefense Security Advisory 08.14.07: Microsoft XML Core Services XMLDOM Memory Corruption Vulnerability



Microsoft XML Core Services XMLDOM Memory Corruption Vulnerability

iDefense Security Advisory 08.14.07
http://labs.idefense.com/intelligence/vulnerabilities/ 
Aug 14, 2007

I. BACKGROUND

XML Core Services (also known as MSXML) is a library for processing XML
files. It works with, and was original part of, Internet Explorer. For
more information visit the following URL.

http://msdn2.microsoft.com/en-us/xml/default.aspx 

http://en.wikipedia.org/wiki/MSXML 

II. DESCRIPTION

Remote exploitation of a buffer overflow vulnerability within Microsoft
Corp.'s XML Core Services may allow an attacker to execute arbitrary
code in the context of the current user.

The vulnerability specifically exists in incorrect checking being
performed on the length argument to the substringData() method of an
XMLDOM object. When certain length values are supplied, a large region
of memory is copied into a buffer of insufficient size.

III. ANALYSIS

Exploitation of this vulnerability requires an attacker to convince a
user to open a page containing a malicious script.

In testing by iDefense Labs, code execution was determined to be
possible. Calling the vulnerable code with no other setup would simply
cause the application to write (or sometimes read) past the end of the
allocated memory and trigger an access violation exception. However, an
attacker can cause pointers in use by another thread to be overwritten
and may be able to execute code.

IV. DETECTION

iDefense confirmed the existence of this vulnerability using Internet
Explorer 6.x on Windows XP SP2. It is suspected that other versions are
also affected.

V. WORKAROUND

Disable active scripting, if it is not necessary for daily operations,
using the following steps.

  1. In IE, click on Tools and select Internet Options from the
drop-down menu.
  2. Click the Security tab and the Custom Level button.
  3. Under Scripting, then Active Scripting, click the Disable radio button.

VI. VENDOR RESPONSE

Microsoft has addressed this vulnerability within Microsoft Security
Bulletins MS07-042 and MS07-043. For more information, consult their
bulletins at the following URLs.

http://www.microsoft.com/technet/security/Bulletin/MS07-042.mspx 

http://www.microsoft.com/technet/security/Bulletin/MS07-043.mspx 

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-2223 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for 
security problems.

VIII. DISCLOSURE TIMELINE

05/17/2006  Initial vendor notification
05/17/2006  Initial vendor response
08/14/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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http://labs.idefense.com/ 

X. LEGAL NOTICES

Copyright =A9 2007 iDefense, Inc.

Permission is granted for the redistribution of this alert
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part of this alert in any other medium other than electronically,
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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
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