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Microsoft Internet Explorer CSS Style Table Layout Uninitialized Memory Vulnerability



Internet Explorer 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 memory corruption vulnerability in Microsoft Corp.'s Internet Explorer could allow an attacker to execute arbitrary code with the privileges of the current user.

The vulnerability exists due to an uninitialized variable in the "CLayout::EnsureDispNode" method. This method is called to recalculate the location of various HTML elements within the page. This function passes a "CDispNodeInfo" object to another function, "CLayout::GetDispNodeInfo," which is supposed to initialize the object passed in; however, the function fails to properly initialize a flag's value that is used later to determine how many "extra" bytes to allocate for a heap buffer. This eventually leads to an undersized buffer being allocated to hold a "CDispClipNode" object in the "CLayout::EnsureDispNodeCore" function. The vulnerability manifests itself when the "CDispNode::SetUserClip" function attempts to use the invalid "extra size" to calculate an offset into the object and manipulate a bit at this location. This corrupts the objects VTABLE by setting the second bit to 1, which can lead to the execution of arbitrary code when this pointer is accessed later.


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. 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.


Microsoft Internet Explorer 6, 7 and 8 are vulnerable.


Microsoft suggested workarounds can be found in Microsoft Security Bulletin MS10-090.


Microsoft Corp. has released patches which address 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-2010-3962 to this issue. This is a candidate for inclusion in the CVE list (, which standardizes names for security problems.


08/11/2010 Initial Vendor Notification
08/11/2010 Initial Vendor Reply
12/14/2010 Coordinated Public Disclosure


This vulnerability was reported to iDefense by José Antonio Vázquez González.

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Copyright © 2010 Verisign, Inc.

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