From labs-no-reply@idefense.com Tue Apr 12 15:58:25 2005 From: iDEFENSE Labs To: bugtraq@securityfocus.com, vulnwatch@vulnwatch.org, full-disclosure@lists.netsys.com Date: Tue, 12 Apr 2005 14:43:39 -0400 Subject: iDEFENSE Security Advisory 04.12.05: Microsoft Internet Explorer DHTML Engine Race Condition Vulnerability Microsoft Internet Explorer DHTML Engine Race Condition Vulnerability iDEFENSE Security Advisory 04.12.05 www.idefense.com/application/poi/display?id=228&type=vulnerabilities April 12, 2005 I. BACKGROUND Internet Explorer is a set of core technologies in Microsoft Windows operating systems that provide web browsing functionality. Further information is available at: http://www.microsoft.com/ie/. Dynamic HTML (DHTML) is built on an object model that extends the traditional static HTML document to enable web authors to create more engaging and interactive Web pages. DHTML provides authors with enhanced creative control so they can manipulate any page element at any time. More information is available at: http://www.microsoft.com/windows/ie http://msdn.microsoft.com/workshop/author/dhtml/dhtml_node_entry.asp II. DESCRIPTION Remote exploitation of a race condition vulnerability in version 6 of Microsoft Corporation's Internet Explorer web browser could allow the execution of arbitrary code under the privileges of the currently logged in user. Internet Explorer supports dynamic creation of HTML elements with JavaScript using various DHTML methods such as createElement(), appendChild(), and removeNode(). A number of problems have been found in the implementation of these objects and methods, including some which can be exploited to cause execution of arbitrary code. The problem specifically exists within the memory management routines of Internet Explorer's object handling code. In some situations one thread reads data from memory that has either been overwritten by another thread or has not yet been initialized by another thread. This can lead to random crashes and remote command execution. III. ANALYSIS Successful exploitation allows remote attackers to execute arbitrary code in the context of the user running the Internet Explorer process. Exploitation will not be 100% reliable. However, proof of concept exploit code was generated with reliable execution approximately 90% of the time. In order to exploit this vulnerability an attacker must convince the victim to visit a web site, or cause malicious DHTML code to be rendered by Internet Explorer using some other technique, such as a persist ant XSS (cross-site scripting) attack on a trusted site. IV. DETECTION iDEFENSE has confirmed the existence of this vulnerability in the following Microsoft Internet Explorer versions: 6.0.2900.2180 on Windows XP Professional with Service Pack 2. 6.0.2800.1106 on Windows XP Professional with Service Pack 1. 6.0.2800.1106 on Windows 2000 Professional with Service Pack 4. It is suspected that all versions of Internet Explorer 6.0 are affected. V. WORKAROUND Disable active scripting, if it is not necessary for daily operations, using the following steps: 1. In IE, click on Tools and select Internet Options from the drop-down menu. 2. Click the Security tab and the Custom Level button. 3. Under Scripting, then Active Scripting, click the Disable radio button. VI. VENDOR RESPONSE This vulnerability is addressed in Microsoft Security Bulletin MS05-020 available at: http://www.microsoft.com/technet/security/Bulletin/MS05-020.mspx VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the names CAN-2005-0553 to these issues. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems. VIII. DISCLOSURE TIMELINE 10/25/2004 Initial vendor notification 10/25/2004 Initial vendor response 04/12/2005 Coordinated public disclosure IX. CREDIT Berend-Jan Wever (skylined[at]edup.tudelft.nl, http://www.edup.tudelft.nl/~bjwever/) is credited with this discovery. Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp Free tools, research and upcoming events http://labs.idefense.com X. LEGAL NOTICES Copyright (c) 2005 iDEFENSE, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customerservice@idefense.com for permission. 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.