__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft Cumulative Patch for Outlook Express [Microsoft Security Bulletin MS03-014] April 24, 2003 20:00 GMT Number N-081 ______________________________________________________________________________ PROBLEM: A vulnerability exists in the MHTML URL Handler that allows any file that can be rendered as text to be opened and rendered as part of a page in Internet Explorer. If the text file contained script, that script would execute when the file was accessed. SOFTWARE: * Microsoft Outlook Express 5.5 * Microsoft Outlook Express 6.0 DAMAGE: Exploiting the vulnerability would allow an attacker the same privileges as the user. SOLUTION: Apply patch as indicated in Microsoft's bulletin. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. An attacker would have to host a web site ASSESSMENT: or send a malicious email that contained a web page used to exploit this vulnerability and entice, or lure, a user to visit it. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/n-081.shtml ORIGINAL BULLETIN: http://www.microsoft.com/technet/treeview/ default.asp?url=/technet/security/bulletin/MS03-014.asp ______________________________________________________________________________ [***** Start Microsoft Security Bulletin MS03-014 *****] Microsoft Security Bulletin MS03-014 Cumulative Patch for Outlook Express (330994) Originally posted: April 23, 2003 Summary Who should read this bulletin: Customers using Outlook Express. Impact of vulnerability: This bulletin addresses a vulnerability that could allow an attacker to run code of the attacker’s choice on a user’s machine. To exploit the vulnerability, attacker would have to be able to cause Windows to open a specially constructed MHTML URL, either on a web site or included in an HTML email message. Maximum Severity Rating: Critical Recommendation: Customers should install the patch at the earliest opportunity. Affected Software: * Microsoft Outlook Express 5.5 * Microsoft Outlook Express 6.0 Technical details Technical description: MHTML stands for MIME Encapsulation of Aggregate HTML. MHTML is an Internet standard that defines the MIME (Multipurpose Internet Mail Extensions) structure used to send HTML content in e-mail message bodies. The MHTML URL Handler in Windows is part of Outlook Express and provides a URL type that can be used on the local machine. This URL type (MHTML://) allows MHTML documents to be launched from a command line, from Start/Run, using Windows Explorer or from within Internet Explorer. A vulnerability exists in the MHTML URL Handler that allows any file that can be rendered as text to be opened and rendered as part of a page in Internet Explorer. As a result, it would be possible to construct a URL that referred to a text file that was stored on the local computer and have that file render as HTML. If the text file contained script, that script would execute when the file was accessed. Since the file would reside on the local computer, it would be rendered in the Local Computer Security Zone. Files that are opened within the Local Computer Zone are subject to fewer restrictions than files opened in other security zones. Using this method, an attacker could attempt to construct a URL and either host it on a website or send it via email. In the web based scenario, where a user then clicked on a URL hosted on a website, an attacker could have the ability to read or launch files already present on the local machine. In the case of an e-mail borne attack, if the user was using Outlook Express 6.0 or Outlook 2002 in their default configurations, or Outlook 98 or 2000 in conjunction with the Outlook Email Security Update, then an attack could not be automated and the user would still need to click on a URL sent in the e-mail. However if the user was not using Outlook Express 6.0 or Outlook 2002 in their default configurations, or Outlook 98 or 2000 in conjunction with the Outlook Email Security Update, the attacker could cause an attack to trigger automatically without the user having to click on a URL contained in an e-mail. In both the web based and e-mail based cases, any limitations on the user’s privileges would also restrict the capabilities of the attacker’s script. Applying the update listed in Microsoft Security Bulletin MS03-004 -- Cumulative Patch for Internet Explorer—will help block an attacker from being able to load a file onto a user’s computer and prevent the passing of parameters to an executable. This means that an attacker could only launch a program that already existed on the computer—provided the attacker was aware of the location of the program—and would not be able to pass parameters to the program for it to execute. MHTML is a standard for exchanging HTML content in e-mail and as a result the MHTML URL Handler function has been implemented in Outlook Express. Internet Explorer can also render MHTML content, however the MHTML function has not been implemented separately in Internet Explorer – it simply uses Outlook Express to render the MHTML content. Mitigating factors: * For the web-based scenario, the attacker would have to host a web site that contained a web page used to exploit this vulnerability and entice a user to visit it. An attacker would have no way to force a user to visit the site. Instead, the attacker would need to lure the user there, typically by getting the user to click on a link to the attacker's site. * The HTML mail-based attack scenario would be blocked by Outlook Express 6.0 and Outlook 2002 in their default configurations, and by Outlook 98 and 2000 if used in conjunction with the Outlook Email Security Update. * Exploiting the vulnerability would allow the attacker only the same privileges as the user. Users whose accounts are configured to have few privileges on the system would be at less risk than ones who operate with administrative privileges. * If the cumulative patch for Internet Explorer MS03-004 has been installed, known means by which an attacker may place a file onto a user’s computer will be blocked. * In order to invoke an executable already present on the local system, an attacker must know the path to that executable. Severity Rating: Outlook Express 5.5 Critical Outlook Express 6.0 Critical The above assessment is based on the types of systems affected by the vulnerability, their typical deployment patterns, and the effect that exploiting the vulnerability would have on them. Vulnerability identifier: CAN-2002-0980 Tested Versions: Microsoft tested Internet Explorer versions 5.01 SP3, 5.5 SP2, 6.0 Gold and 6.0 SP1 as well as Outlook Express versions 5.5 SP2, 6.0 Gold and 6.0 SP1 for this vulnerability. Versions of IE prior to 5.01 Service Pack 3 are no longer eligible for hotfix support. More information on Windows Operating System Components Lifecycles is available from: http://microsoft.com/windows/lifecycle/desktop/consumer/components.mspx. Patch availability Download locations for this patch * Microsoft Outlook Express http://www.microsoft.com/windows/ie/downloads/critical/330994/default.asp Additional information about this patch Installation platforms: This patch can be installed on systems running: * The OE 5.5 SP2 patch can be installed on systems running Internet Explorer 5.5 Service Pack 2 Windows 98 SE, Windows Millenium, Windows NT 4.0 Service Pack 6a, Windows 2000 Service Pack 2 and Windows 2000 Service Pack 3. * The OE 6.0 patch can be installed on systems running Windows XP Gold. * The OE 6.0 SP1 patch can be installed on system running Internet Explorer 6.0 Service Pack 1 on Windows 98 SE, Windows Millenium, Windows NT 4.0 Service Pack 6a, Windows 2000 Service Pack 2, Windows 2000 Service Pack 3, and Windows XP Service Pack 1 Inclusion in future service packs: The fix for this issue will be included in Internet Explorer 6.0 Service Pack 2. Reboot needed: No Patch can be uninstalled: Yes Superseded patches: This is a cumulative patch for Outlook Express, and includes the fix described in Microsoft Security Bulletin MS02-058. Verifying patch installation: * To verify that the patch has been installed on the machine, open IE, select Help, then select About Internet Explorer and confirm that Q330994 is listed in the Update Versions field. * To verify the individual files, use the patch manifest provided in Knowledge Base article 330994. Caveats: None Localization: Localized versions of this patch are available at the locations discussed in “Patch Availability”. Obtaining other security patches: Patches for other security issues are available from the following locations: * Security patches are available from the Microsoft Download Center, and can be most easily found by doing a keyword search for "security_patch". * Patches for consumer platforms are available from the WindowsUpdate web site Other information: Support: * Microsoft Knowledge Base article 330994 discusses this issue. Knowledge Base articles can be found on the Microsoft Online Support web site. * Technical support is available from Microsoft Product Support Services. There is no charge for support calls associated with security patches. Security Resources: The Microsoft TechNet Security Web Site provides additional information about security in Microsoft products. Disclaimer: The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply. Revisions: * V1.0 April 23, 2003: Bulletin Created. [***** End Microsoft Security Bulletin MS03-014 *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft Corporation for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ Anonymous FTP: ftp.ciac.org PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 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