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Multiple Vendor WebKit column-span RenderButton.m_inner Use-after-Free Vulnerability



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


Remote exploitation of a use-after-free vulnerability in WebKit, as included with multiple vendors' browsers, could allow an attacker to execute arbitrary code with the privileges of the current user. This vulnerability occurs when manipulating the DOM tree via asynchronous JavaScript Event Handlers.


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.


iDefense has confirmed the existence of this vulnerability in the following applications that use Webkit:

  • Safari 5.1.2 on Windows XP and OS X Lion
  • Safari 5.1.5 on Windows XP and OS X Lion
  • MobileSafari on an iPad 1, iOS 5.0.1
  • Chrome 16.0.912.75 m on Windows 7


Disabling JavaScript is an effective workaround for this vulnerability. However, disabling scripting can severely impact the usability of the browser.


Apple Inc. has released an update which addresses this issue. For more information, consult their advisory at the following URL:


The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2012-1520 to this issue. This is a candidate for inclusion in the CVE list (, which standardizes names for security problems.


04/04/2012 Initial Vendor Notification
04/04/2012 Initial Vendor Reply
07/25/2012 Coordinated Public Disclosure


This vulnerability was reported to iDefense by Jose A. Vazquez of

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Copyright © 2012 Verisign, Inc.

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