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Multiple Vendor WebKit XML 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 Apple Inc.'s Safari Web browser and Google Inc.'s Chrome Web browser, could allow an attacker to execute arbitrary code with the privileges of the current user.

The vulnerability occurs during the processing of Style Sheet elements. Specifically, it is possible to trigger a use-after-free vulnerability when Safari fails to properly release an object. The object's memory is freed; however, a reference to the object remains. When the reference is later used to access the object, this now invalid memory is treated as a valid object and the object's vtable is used to make an indirect function call. This may result in 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 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 Apple products and versions are vulnerable:

  • Safari versions 5.1 and prior
  • iOS 3.0 through 4.3.5 for iPhone 3GS and iPhone 4
  • iOS 3.1 through 4.3.5 for iPod touch (3rd generation) and later
  • iOS 3.2 through 4.3.5 for iPad


iDefense is unaware of any available workarounds for this issue.


Apple Inc. has released patches 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-2011-2341 to this issue. This is a candidate for inclusion in the CVE list (, which standardizes names for security problems.


04/13/2011 Initial Vendor Notification
04/15/2011 Initial Vendor Reply
11/15/2011 Coordinated Public Disclosure


This vulnerability was reported to iDefense by wushi of team509.

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Copyright © 2011 Verisign, Inc.

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