iDefense Security Advisory 06.07.10: Multiple Vendor WebKit HTML Caption Use After Free Vulnerability

iDefense Security Advisory 06.07.10
http://labs.idefense.com/intelligence/vulnerabilities/
Jun 07, 2010

I. BACKGROUND

WebKit is an open source web browser engine. It is currently used by
Apple Inc.'s Safari browser, as well as by Google's Chrome browser. For
more information, see the vendor's site at the following link.

http://webkit.org/

II. DESCRIPTION

Remote exploitation of a memory corruption vulnerability in WebKit, as
included with multiple vendors' browsers, could allow an attacker to
execute arbitrary code with the privileges of the current user. Google
Chrome browsers to parse and render web content.

The vulnerability occurs when the a certain property of an HTML element
with a caption is reset via JavaScript code. When this occurs, a C++
object is incorrectly accessed after it has been freed. This results in
an attacker controlled value being used as a C++ VTABLE, which leads to
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 webpage
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

iDefense has confirmed the existence of this vulnerability in Google
Chrome (3.0.195.38 and 4.0.249.78), and Safari 4.0.4 (Windows XP/OS X
10.5.8). Previous versions are suspected to be vulnerable, as are any
other browsers or applications that make use of the WebKit engine.
Safari versions prior to 4.1 and 5.0 are vulnerable.

V. WORKAROUND

The vulnerability is present in the JavaScript engine, so disabling
JavaScript is an effective workaround. This can be performed via the
command line with Google Chrome, and the Preferences menu in Safari.

VI. VENDOR RESPONSE

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

http://www.apple.com/safari/download/

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2010-1400 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

01/28/2010 Initial Vendor Notification
01/28/2010 Initial Vendor Reply
06/07/2010 Coordinated Public Disclosure

IX. CREDIT

This vulnerability was reported to iDefense by wushi of team509.

Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php

Free tools, research and upcoming events
http://labs.idefense.com/

X. LEGAL NOTICES

Copyright © 2010 iDefense, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDefense. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically,
please e-mail [email protected] for permission.

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.