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Multiple Vendor WebKit SVG Element 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 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. WebKit is an open source web browser engine.

This vulnerability occurs when the WebKit parsing code fails to handle an invalid sequence of style tags embedded within an SVG group element. The sequence of tags is not valid according to the HTML 4 schema, and this triggers an error during parsing. When handling this error, a pointer to an SVG element is freed. However, a reference to this object remains in an array accessed elsewhere. Later, this stale reference is accessed, resulting in use-after-free vulnerability that can lead to arbitrary code execution.


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.


The following vendors include susceptible packages within their respective software distributions:

  • Apple Inc.: :iPhone 3GS, iPhone 4, iPhone 4S, iPod touch (3rd generation) and later, iPad, iPad 2 running iOS version prior to 5.1, iTunes prior to 10.6, Safari prior to 5.1.4
  • Google Inc.: Chrome versions prior to 14.0.835.163


iDefense is currently unaware of any workaround for this issue.


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

iTunes: Safari: iOS:


The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2011-2855 to this issue. This is a candidate for inclusion in the CVE list (, which standardizes names for security problems.


12/28/2011 Initial Vendor Notification
12/29/2011 Initial Vendor Reply
03/07/2012 Coordinated Public Disclosure


This vulnerability was reported to iDefense by wushi of team509.

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Copyright © 2012 Verisign, Inc.

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