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Multiple Vendor WebKit HTML Caption Use After Free Vulnerability



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.


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.


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.


iDefense has confirmed the existence of this vulnerability in Google Chrome ( and, 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.


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.


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


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 (, which standardizes names for security problems.


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


This vulnerability was reported to iDefense by wushi of team509.

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Copyright © 2010 Verisign, Inc.

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