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                        National Cyber Alert System

                  Technical Cyber Security Alert TA04-293A


Multiple Vulnerabilities in Microsoft Internet Explorer

   Original release date: October 19, 2004
   Last revised: --
   Source: US-CERT


Systems Affected

   Microsoft Windows systems running

     * Internet Explorer versions 5.01 and later; previous,
       unsupported versions of Internet Explorer may also be affected

     * Programs that use the WebBrowser ActiveX control (WebOC) or
       MSHTML rendering engine


Overview

   Microsoft Internet Explorer (IE) contains multiple vulnerabilities,
   the most severe of which could allow a remote attacker to execute
   arbitrary code with the privileges of the user running IE.


I. Description

   Microsoft Security Bulletin MS04-038 describes a number of IE
   vulnerabilities, including buffer overflows, cross-domain
   scripting, spoofing, and "drag and drop." Further details are
   available in the following vulnerability notes:

 * VU#291304 - Microsoft Internet Explorer contains a buffer overflow
   in CSS parsing
 
    A buffer overflow vulnerability exists in the way that IE
    processes Cascading Style Sheets (CSS). This could allow an
    attacker to execute arbitrary code or cause a denial of service.
    (CAN-2004-0842)

 * VU#637760 - Microsoft Internet Explorer Install Engine contains a
   buffer overflow vulnerability

    The IE Active Setup Install Engine (inseng.dll), which is used to
    decompress ActiveX controls stored in CAB files, contains a buffer
    overflow vulnerability. This could allow an attacker to execute
    arbitrary code. (CAN-2004-0216)

 * VU#207264 - Microsoft Internet Explorer does not properly handle
   function redirection (Similar Method Name Redirection Cross Domain
   Vulnerability)

    IE does not properly validate redirected functions. The impact is
    similar to that of a cross-site scripting vulnerability, allowing
    an attacker to access data and execute script in other domains,
    including the Local Machine Zone. (CAN-2004-0727)

 * VU#526089 - Microsoft Internet Explorer treats arbitrary files as
   images for drag and drop operations (Drag and Drop Vulnerability)

    IE treats arbitrary files as images during "drag and drop" mouse
    operations. This could allow an attacker to trick a user into
    copying a file to a location where it could be executed, such as
    the user's Startup folder. (CAN-2004-0839)

 * VU#413886 - Microsoft Internet Explorer allows mouse events to
   manipulate window objects and perform "drag and drop" operations
   (Script in Image Tag File Download Vulnerability, HijackClick 3)

    IE dynamic HTML (DHTML) mouse events can manipulate windows to
    copy objects from one domain to another, including the Local
    Machine Zone.  This could allow an attacker to write an arbitrary
    file to the local file system in a location where it could be
    executed, such as the user's Startup folder. (CAN-2004-0841)

   In addition, MS04-038 describes two address bar spoofing
   vulnerabilities (VU#625616, VU#431576) that could allow an attacker
   to deceive a user about the location of a web site; a vulnerability
   involving cached HTTPS files (VU#795720) that could allow an
   attacker to read from or inject data into an HTTPS web site; and a
   vulnerability in which IE6 on Windows XP ignores the "Drag and drop
   and copy and paste files" setting (VU#630720).

   Any program that uses the WebBrowser ActiveX control (WebOC) or
   MSHTML rendering engine could be affected by these vulnerabilities.


II. Impact

   The impacts of these vulnerabilities vary, but an attacker may be
   able to execute arbitrary code with the privileges of the user
   running IE.  An attacker could also exploit these vulnerabilities
   to perform social engineering attacks such as spoofing or phishing
   attacks. In most cases, an attacker would need to convince a user
   to view an HTML document (web page, HTML email message) with IE or
   another program that uses the WebBrowser ActiveX control or MSHTML
   rendering engine.

   In some cases, an attacker could combine two or more
   vulnerabilities to write an arbitrary file to the local file system
   in a sensitive location, such as the user's Startup folder. US-CERT
   has monitored reports of attacks against some of these
   vulnerabilities.


III. Solution

Apply a patch

   Apply the appropriate patch as specified by Microsoft Security
   Bulletin MS04-038.

Disable Active scripting and ActiveX controls

   To protect from attacks against several of these vulnerabilities,
   disable Active scripting and ActiveX controls in any zone used to
   render untrusted HTML content (typically the Internet Zone and
   Restricted Sites Zone). Instructions for disabling Active scripting in
   the Internet Zone can be found in the Malicious Web Scripts FAQ.

Upgrade to Windows XP Service Pack 2

   Service Pack 2 for Windows XP contains security improvements for IE
   that reduce the impact of some of these vulnerabilities.


Appendix A. References

     * Vulnerability Note VU#291304 -
       <http://www.kb.cert.org/vuls/id/291304>

     * Vulnerability Note VU#637760 -
       <http://www.kb.cert.org/vuls/id/637760>

     * Vulnerability Note VU#207264 -
       <http://www.kb.cert.org/vuls/id/207264>

     * Vulnerability Note VU#526089 -
       <http://www.kb.cert.org/vuls/id/526089>

     * Vulnerability Note VU#413886 -
       <http://www.kb.cert.org/vuls/id/413886>

     * Vulnerability Note VU#625616 -
       <http://www.kb.cert.org/vuls/id/625616>

     * Vulnerability Note VU#431576 -
       <http://www.kb.cert.org/vuls/id/431576>

     * Vulnerability Note VU#795720 -
       <http://www.kb.cert.org/vuls/id/795720>

     * Vulnerability Note VU#630720 -
       <http://www.kb.cert.org/vuls/id/630720>

     * Vulnerability Note VU#673134 -
       <http://www.kb.cert.org/vuls/id/673134>

     * Malicious Web Scripts FAQ -
       <http://www.cert.org/tech_tips/malicious_code_FAQ.html>

     * Microsoft Security Bulletin MS04-038 -
       <http://www.microsoft.com/technet/security/bulletin/ms04-038.mspx>

     _________________________________________________________________

   Information used in this document came from Microsoft Security
   Bulletin MS04-038. Microsoft credits Greg Jones, Peter Winter-Smith,
   Mitja Kolsek, and John Heasman for reporting several vulnerabilities.
   Will Dormann reported the IE6 Windows XP drag and drop setting
   vulnerability.
     _________________________________________________________________

   Feedback can be directed to the authors: Art Manion and Will Dormann.
     _________________________________________________________________


   This document is available from:

     <http://www.us-cert.gov/cas/techalerts/TA04-293A.html>

     _________________________________________________________________

   Copyright 2004 Carnegie Mellon University.

   Terms of use:

     <http://www.us-cert.gov/legal.html>
     _________________________________________________________________


   Revision History

   October 19, 2004: Initial release

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