iDefense Security Advisory 10.11.11: Microsoft Internet Explorer Object Handling Memory Corruption Vulnerability

iDefense Security Advisory 10.11.11
http://labs.idefense.com/intelligence/vulnerabilities/
Oct 11, 2011

I. BACKGROUND

Internet Explorer is a graphical web browser developed by Microsoft
Corp. that has been included with Microsoft Windows since 1995. For more
information about Internet Explorer, please the visit following website:
http://www.microsoft.com/windows/internet-explorer/default.aspx

II. DESCRIPTION

Remote exploitation of a memory corruption vulnerability in Microsoft
Corp.'s Internet Explorer could allow an attacker to execute arbitrary
code with the privileges of the current user.

The vulnerability occurs when a Javascript event handler such as
"onload" is set to a Javascript object's attributes or childNodes
collection. A event object is created and this object's memory is later
freed; however, a reference to the object remains. When the reference is
later used to access the event object, this now-invalid memory is
treated as a valid object. The corrupt object's vtable is used to make
an indirect function call. This may result in the execution of arbitrary
code.

III. ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary
code with the privileges of the user viewing the Web page. To exploit
this vulnerability, a targeted user must load a malicious Web page
created by an attacker. An attacker typically accomplishes this via
social engineering or injecting content into compromised, trusted sites.
After the user visits the malicious Web page, no further user
interaction is needed.

IV. DETECTION

Microsoft Internet Explorer 6 is vulnerable.

V. WORKAROUND

Microsoft suggested workarounds can be found under the workaround
section of the following link:

http://www.microsoft.com/technet/security/bulletin/MS11-081.mspx

VI. VENDOR RESPONSE

Microsoft has released fixes which addresses this issue. Information
about downloadable vendor updates can be found by clicking on the URLs
shown.

http://www.microsoft.com/technet/security/bulletin/MS11-081.mspx

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2011-1997 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

06/08/2011 Initial Vendor Notification
06/08/2011 Vendor Reply
10/11/2011 Coordinated Public Disclosure

IX. CREDIT

This vulnerability was reported to iDefense by gwslabs.com.

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X. LEGAL NOTICES

Copyright A© 2011 Verisign

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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.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.