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Microsoft Internet Explorer HTML TIME 'ondatasetcomplete' Use After Free Vulnerability

28.07.09

BACKGROUND

HTML+TIME (HTML Timed Interactive Multimedia Extensions)is a web standard that was created for Microsoft Corp.'s Internet Explorer (IE) to allow web page authors to create timed animation content on a web page. This is accomplished using an XML like markup that makes use of HTML+TIME properties and elements. Internet Explorer supports this markup standard, and also exposes a scripting interface for interacting with the HTML+TIME elements on the page. For more information, please see the vendor's web page at the following link:

http://technet.microsoft.com/en-us/library/ms533099(VS.85).aspx

DESCRIPTION

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.

The vulnerability occurs when the 'ondatasetcomplete' event method of a timeChildren object is referenced. If this occurs when the object is in an inconsistent state, a heap chunk will be freed, and then reused after being freed. This results in an uninitialized VTABLE being used, which can result in the execution of arbitrary code when the pointer is dereferenced.

ANALYSIS

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.

DETECTION

iDefense has confirmed the existence of this vulnerability in Internet Explorer versions 6, 7, and 8. Internet Explorer 5 does not appear to be vulnerable.

WORKAROUND

Since this vulnerability is triggered through script code, disabling Active Scripting will prevent the exploitation of this vulnerability.

VENDOR RESPONSE

Microsoft Corp. has released an Out-Of-Band patch which addresses this issue. Information about downloadable vendor updates can be found by clicking on the URLs shown.

http://www.microsoft.com/technet/security/Bulletin/MS09-034.mspx

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2009-1917 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

05/06/2009 - PoC Requested
06/06/2009 - PoC Sent
06/24/2009 - Tentative disclosure set to August
06/25/2009 - Requested CVE from vendor
06/25/2009 - Received CVE from vendor
07/23/2009 - Received updated disclosure notice for OOB in July
07/28/2009 - Coordinated public disclosure

CREDIT

This vulnerability was reported to iDefense by Peter Vreugdenhil.

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LEGAL NOTICES

Copyright © 2009 Verisign, Inc.

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Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.