Microsoft Security Bulletin MS04-009 Vulnerability in Microsoft Outlook Could Allow Code Execution (828040) Issued: March 9, 2004 Version: 1.0 Summary Who Should Read This Document: Customers that are using Microsoft® Office XP and Outlook 2002 Impact of Vulnerability: Remote Code Execution Maximum Severity Rating: Important Recommendation: Customers should install the patch at the earliest opportunity. Security Update Replacement: None Caveats: None Tested Software and Security Update Download Locations: Affected Software Microsoft Office XP Service Pack 2- Download the update Microsoft Outlook 2002 Service Pack 2- Download the update Non Affected Software Microsoft Office 2000 Service Pack 3 Microsoft Office XP Service Pack 3 Microsoft Office 2003 Microsoft Outlook 2000 Service Pack 3 Microsoft Outlook 2002 Service Pack 3 Microsoft Outlook 2003 The software listed above has been tested to determine if the versions are affected. Other versions either no longer include security patch support or may not be affected. Please review the Microsoft Support Lifecycle Web site to determine the support lifecycle for your product and version. Top of section General Information Technical details Technical description: A security vulnerability exists within Outlook 2002 that could allow Internet Explorer to execute script code in the Local Machine zone on an affected system. The parsing of specially crafted mailto URLs by Outlook 2002 causes this vulnerability. To exploit this vulnerability, an attacker would have to host a malicious Web site that contained a Web page designed to exploit the vulnerability and then persuade a user to view the Web page. The attacker could also create an HTML e-mail message designed to exploit the vulnerability and persuade the user to view the HTML e-mail message. After the user has visited the malicious Web site or viewed the malicious HTML e-mail message an attacker who successfully exploited this vulnerability could access files on a user's system or run arbitrary code on a user's system. This code would run in the security context of the currently logged-on user. Outlook 2002 is available as a separate product and is also included as part of Office XP. Mitigating factors: When an Outlook profile is first created and at least one e-mail account is set up during the initial configuration of the profile the default folder home page is automatically changed from "Outlook Today" to "Inbox." Users are only at risk from this vulnerability when the "Outlook Today" home page is their default folder home page. This is the default configuration when an Outlook profile is created without any e-mail accounts. Users are only at risk from this vulnerability when Outlook 2002 is configured as the default mail reader and when the "Outlook Today" home page is their default folder home page. Installing other e-mail clients may change this configuration as they can register themselves as the default mail reader on the system. If an attacker exploited this vulnerability, the attacker would gain 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 users who operate with administrative privileges. Severity Rating: Microsoft Office XP Important Microsoft Outlook 2002 Important The above assessment is based on the types of systems that are affected by the vulnerability, their typical deployment patterns, and the effect that exploiting the vulnerability would have on them. Vulnerability identifier: CAN-2004-0121 Top of section Workarounds Microsoft has tested the following workarounds. These workarounds will not correct the underlying vulnerability. However, they help block known attack vectors. Workarounds may reduce functionality in some cases; in such cases, the reduction in functionality is identified below. Do not use "Outlook Today" as the default home page in Outlook 2002 You can help protect against this vulnerability by changing your default folder home page in Outlook 2002 to the "Inbox" or some other folder than "Outlook Today". The "Outlook Today" home page is only the default folder home page when an Outlook profile is originally configured without any e-mail accounts. 1. In Outlook 2002, click Options in the Tools menu. 2. Under the tab Other choose Advanced Options. 3. Set your "Startup in this folder:" to Inbox if it is set to Outlook Today. Impact of Workaround: The "Outlook Today" folder home page would not be the default view. If you are using Outlook 2002 or Outlook Express 6.0 SP1 or later, read e-mail messages in plain text format to help protect yourself from the HTML e-mail attack vector Microsoft Outlook 2002 users who have applied Service Pack 1 or later and Outlook Express 6.0 users who have applied Service Pack 1 or later can enable a feature that will enable them to view all non-digitally-signed e-mail messages or non-encrypted e-mail messages in plain text only. Digitally-signed e-mail messages and encrypted e-mail messages are not affected by the setting and may be read in their original formats. See Microsoft Knowledge Base Article 307594 for information about how to enable this setting in Outlook 2002. See Microsoft Knowledge Base Article 291387for information about how to enable this setting in Outlook Express 6.0 Impact of Workaround: E-mail that is viewed in plain text format cannot contain pictures, specialized fonts, animations, or other rich content. Additionally: The changes are applied to the preview pane and to open messages. Pictures become attachments to avoid loss of message content. Because the message is still in Rich Text Format or in HTML format in the store, the object model (custom code solutions) may behave unexpectedly because the message is still in Rich Text Format or in HTML format in the mail store. Acknowledgments Microsoft thanks the following for working with us to help protect customers: iDefense and Jouko Pynnönen for reporting the issue described in MS04-009. Obtaining other security updates: Updates for other security issues are available from the following locations: Security updates are available from the Microsoft Download Center, and can be most easily found by doing a keyword search for "security_patch". Updates for consumer platforms are available from the Windows Update Web site. Support: Technical support is available from Microsoft Product Support Services at 1-866-PCSAFETY for customers in the U.S. and Canada. There is no charge for support calls that are associated with security updates. International customers can get support from their local Microsoft subsidiaries. There is no charge for support associated with security updates. Information on how to contact Microsoft support is available at the International Support Web Site. Security Resources: The Microsoft TechNet Security Web Site provides additional information about security in Microsoft products. Microsoft Software Update Services Microsoft Baseline Security Analyzer (MBSA) Windows Update Windows Update Catalog: Please view Knowledge Base Article 323166 for more information on the Windows Update Catalog. Office Update Systems Management Server (SMS): Systems Management Server can provide assistance deploying this security update. For information about Systems Management Server visit the SMS Web Site. For detailed information about the many enhancements to the security update deployment process that SMS 2003 provides, please visit the SMS 2003 Security Patch Management Web site. Some software updates may require administrative rights following a restart of the computer. 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 (March 9, 2004): Bulletin published