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Microsoft Internet Explorer CBlockElement Use-after-Free Vulnerability



Internet Explorer (IE) is a graphical Web browser developed by Microsoft Corp. that has been included with Microsoft Windows since 1995. For more information about Internet Explorer, please the visit following website:


Remote exploitation of a use-after-free vulnerability in Microsoft Corp.'s Internet Explorer could allow an attacker to execute arbitrary code with the privileges of the current user. A use-after-free vulnerability exists within the way certain CBlockElements are handled in Microsoft Internet Explorer. This issue can be triggered by manipulating the HTML elements within a website using JavaScript.


Exploitation of this issue would result in the execution of arbitrary code with the privileges of the current user. An attacker can exploit this issue by manipulating the heap layout of the browser and triggering the vulnerability. To exploit this issue, an attacker must control the memory that has been freed prior to triggering a reference to that memory. Heap spraying can be used to obtain control of the necessary memory. If successful, the attacker would be able to execute arbitrary code as the current user. An attacker would need to entice a victim into visiting a specially crafted Web page either by e-mail or instant message; then, upon visiting the page, exploitation would occur.


Internet Explorer 8, 9 and 10 are vulnerable.


Vendor Provided:

  • Set Internet and Local intranet security zone settings to "High" to block ActiveX Controls and Active Scripting in these zones
  • Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and local intranet security zone


Microsoft has released a fix 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-2013-3163 to this issue. This is a candidate for inclusion in the CVE list (, which standardizes names for security problems.


12/27/2012 Initial Vendor Notification
12/27/2012 Initial Vendor Reply
07/09/2013 Coordinated Public Disclosure


This vulnerability was reported to iDefense by Jose A. Vazquez of Yenteasy - Security Research.

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Copyright © 2013 Verisign, Inc.

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