__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft Vulnerability in HTML Help Could Allow Code Execution [Microsoft Security Bulletin MS04-023] July 14, 2004 17:00 GMT Number O-182 ______________________________________________________________________________ PROBLEM: The HTML Help protocol does not correctly validate .chm files in Microsoft Help. The HTML protocol is used to open compiled HTML Help files. Microsoft HTML Help is the standard help system for the Windows platform. PLATFORM: Microsoft Windows 2000 Service Pack 2, Microsoft Windows 2000 Service Pack 3, Microsoft Windows 2000 Service Pack 4 Microsoft Windows XP and Microsoft Windows XP Service Pack 1 Microsoft Windows XP 64-Bit Edition Service Pack 1 Microsoft Windows XP 64-Bit Edition Version 2003 Microsoft Windows Server 2003 Microsoft Windows Server 2003 64-Bit Edition Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), Microsoft Windows Millennium Edition (Me) Internet Explorer 6.0 Service Pack 1 when installed on Windows NT 4.0 SP6a (Workstation, Server, or Terminal Server Edition) DAMAGE: If a user is logged on with administrative privileges, an attacker who successfully exploited the most severe of these vulnerabilities could take complete control of an affected system, including installing programs; viewing, changing, or deleting data; or creating new accounts that have full privileges. SOLUTION: Install the security update. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. A remote attacker may execute code and gain ASSESSMENT: root privileges by hosting a malicious website and enticing a user to view the site or access the site via an HTML email message. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/o-182.shtml ORIGINAL BULLETIN: http://www.microsoft.com/technet/security/bulletin/ ms04-023.mspx CVE/CAN: http://www.cve.mitre.org/cgi-bin/cvename.cgi?name= CAN-2003-1041, CAN-2004-0201 ______________________________________________________________________________ [***** Start Microsoft Security Bulletin MS04-023 *****] Microsoft Security Bulletin MS04-023 Vulnerability in HTML Help Could Allow Code Execution (840315) Issued: July 13, 2004 Version: 1.0 Summary Who should read this document: Customers who use Microsoft Windows Impact of Vulnerability: Remote Code Execution Maximum Severity Rating: Critical Recommendation: Customers should apply the update immediately. Security Update Replacement: None Caveats: Windows NT Workstation 4.0, Windows NT Server 4.0 and Windows NT 4.0 Terminal Server Edition are not affected by default. However if you have installed Internet Explorer 5.5 Service Pack 2 or Internet Explorer 6.0 Service Pack 1 you will have the vulnerable component on your system. Tested Software and Security Update Download Locations: Affected Software: • Microsoft Windows 2000 Service Pack 2, Microsoft Windows 2000 Service Pack 3, Microsoft Windows 2000 Service Pack 4 – Download the update • Microsoft Windows XP and Microsoft Windows XP Service Pack 1 – Download the update • Microsoft Windows XP 64-Bit Edition Service Pack 1 – Download the update • Microsoft Windows XP 64-Bit Edition Version 2003 – Download the update • Microsoft Windows Server™ 2003 – Download the update • Microsoft Windows Server 2003 64-Bit Edition – Download the update • Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and Microsoft Windows Millennium Edition (Me) – Review the FAQ section of this bulletin for details about these operating systems. Non-Affected Software: • Microsoft Windows NTฎ Workstation 4.0 Service Pack 6a • Microsoft Windows NT Server 4.0 Service Pack 6a • Microsoft Windows NT Server 4.0 Terminal Server Edition Service Pack 6 Tested Microsoft Windows Components: Affected Components: • Internet Explorer 6.0 Service Pack 1 when installed on Windows NT 4.0 SP6a (Workstation, Server, or Terminal Server Edition) - Download the update The software in this list has been tested to determine if the versions are affected. Other versions either no longer include security update support or may not be affected. To determine the support lifecycle for your product and version, visit the following Microsoft Support Lifecycle Web site. Top of section General Information Executive Summary Executive Summary: This update resolves two newly-discovered vulnerabilities. The HTML Help vulnerability was privately reported and the showHelp vulnerability is public. Each vulnerability is documented in this bulletin in its own Vulnerability Details section. If a user is logged on with administrative privileges, an attacker who successfully exploited the most severe of these vulnerabilities could take complete control of an affected system, including installing programs; viewing, changing, or deleting data; or creating new accounts that have full privileges. Users whose accounts are configured to have fewer privileges on the system would be at less risk than users who operate with administrative privileges. We recommend that customers apply the update immediately. Severity Ratings and Vulnerability Identifiers: Vulnerability Identifiers - showHelp Vulnerability - CAN-2003-1041 Impact of Vulnerability - Remote Code Execution Windows 98,98 SE,ME - Not Critical Windows NT 4.0 - Important Windows 2000 - ImportantWindows XP - Important Windows Server 2003 - Important Vulnerability Identifiers - HTML Help Vulnerability - CAN-2004-0201 Impact of Vulnerability - Remote Code Execution Windows 98,98 SE,ME - Critical Windows NT 4.0 - Critical Windows 2000 - CriticalWindows XP - Critical Windows Server 2003 - Critical Vulnerability Identifiers - Aggregate Severity of All Vulnerabilities Windows 98,98 SE,ME - Critical Windows NT 4.0 - Critical Windows 2000 - CriticalWindows XP - Critical Windows Server 2003 - Critical This 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. Top of section Frequently asked questions (FAQ) related to this security update Top of section Vulnerability Details showHelp Vulnerability - CAN-2003-1041: A remote code execution vulnerability exists in the processing of a specially crafted showHelp URL. The vulnerability could allow malicious code to run in the Local Machine security zone in Internet Explorer, which could allow an attacker to take complete control of an affected system. Mitigating Factors for showHelp Vulnerability - CAN-2003-1041: • To exploit this vulnerability an attacker would have to use a specially crafted file that is at a known location on the target system. • In a Web-based attack scenario, an attacker would have to host a Web site that contains a Web page that is used to exploit this vulnerability. An attacker would have no way to force users to visit a malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site. After they click the link, they would be prompted to perform several actions. An attack could only occur after they performed these actions. • An attacker who successfully exploited this vulnerability could gain the same privileges as the user. Users whose accounts are configured to have fewer privileges on the system would be at less risk than users who operate with administrative privileges. • By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. The Restricted sites zone helps reduce attacks that could attempt to exploit this vulnerability. The risk of attack from the HTML e-mail vector can be significantly reduced if you meet all the following conditions: • Apply the update that is included with Microsoft Security Bulletin MS03-040 or a later Cumulative Security Update for Internet Explorer. • Use Internet Explorer 6 or later. • Use the Microsoft Outlook E-mail Security Update, use Microsoft Outlook Express 6 or later, or use Microsoft Outlook 2000 Service Pack 2 or later in its default configuration. Top of section Workarounds for showHelp Vulnerability - CAN-2003-1041: Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified below. • Strengthen the security settings for the Local Machine zone in Internet Explorer Because this vulnerability permits an attacker to run HTML code in the Local Machine security zone, users can reduce the impact of this vulnerability by restricting the default settings in this zone. For more information about these settings, and for more information about the potential impacts of changing these default settings, see Microsoft Knowledge Base Article 833633. Warning: Microsoft recommends that customers consider these changes to Internet Explorer security settings as a last resort only. If you make these changes, you may lose some functionality for some Windows programs and components. Before you make these changes in a production environment, test the changes extensively to verify that mission-critical programs continue to work correctly for all users. • Unregister HTML Help To unregister the HTML Help protocol, follow these steps: 1. Click Start, click Run, type "regsvr32 /u %windir%\system32\itss.dll" (without the quotation marks), and then click OK. Note On Windows 98 and Windows Me, replace "system32" with "system" in this command. 2. A dialog box appears to confirm that the unregistration process has succeeded. Click OK to close the dialog box. Impact of Workaround: All HTML Help functionality will be unavailable. This will affect the online Help in Windows or any application that uses HTML Help functionality. • Read e-mail messages in plain text format if you are using Outlook 2002 or later, or Outlook Express 6 SP1 or later, to help protect yourself from the HTML e-mail attack vector. Microsoft Outlook 2002 users who have applied Office XP Service Pack 1 or later and Microsoft Outlook Express 6 users who have applied Internet Explorer 6 Service Pack 1 can enable this setting and view e-mail messages that are not digitally signed or e-mail messages that are not encrypted in plain text only. Digitally signed e-mail messages or encrypted e-mail messages are not affected by the setting and may be read in their original formats. For more information about enabling this setting in Outlook 2002, see Microsoft Knowledge Base Article 307594. For information about this setting in Outlook Express 6, see Microsoft Knowledge Base Article 291387. Impact of Workaround: E-mail messages that are viewed in plain text format will not contain pictures, specialized fonts, animations, or other rich content. In addition: • The changes are applied to the preview pane and to open messages. • Pictures become attachments so that they are not lost. • Because the message is still in Rich Text or HTML format in the store, the object model (custom code solutions) may behave unexpectedly. Top of section FAQ for showHelp Vulnerability - CAN-2003-1041: Top of section Top of section HTML Help Vulnerability – CAN-2004-0201 A remote code execution vulnerability exists in HTML Help that could allow remote code execution on an affected system. If a user is logged on with administrative privileges, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full privileges. Users whose accounts are configured to have fewer privileges on the system would be at less risk than users who operate with administrative privileges Mitigating Factors for HTML Help Vulnerability - CAN-2004-0201: • In a Web-based attack scenario, an attacker would have to host a Web site that contains a Web page that is used to exploit this vulnerability. An attacker would have no way to force users to visit a malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site. • An attacker who successfully exploited this vulnerability could gain the same privileges as the user. Users whose accounts are configured to have fewer privileges on the system would be at less risk than users who operate with administrative privileges. Top of section Workarounds for HTML Help Vulnerability - CAN-2004-0201: Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified below. • Unregister HTML Help To unregister the HTML Help protocol, follow these steps: 1. Click Start, click Run, type "regsvr32 /u %windir%\system32\itss.dll" (without the quotation marks), and then click OK. Note On Windows 98 and Windows Me, replace "system32" with "system" in this command. 2. A dialog box appears to confirm that the unregistration process has succeeded. Click OK to close the dialog box. Impact of Workaround: All HTML Help functionality will be unavailable. This will affect the online Help in Windows or in any application that use HTML Help functionality. • Read e-mail messages in plain text format if you are using Outlook 2002 or later, or Outlook Express 6 SP1 or later, to help protect yourself from the HTML e-mail attack vector. Microsoft Outlook 2002 users who have applied Office XP Service Pack 1 or later and Microsoft Outlook Express 6 users who have applied Internet Explorer 6 Service Pack 1 can enable this setting and view e-mail messages that are not digitally signed or e-mail messages that are not encrypted in plain text only. Digitally signed e-mail messages or encrypted e-mail messages are not affected by the setting and may be read in their original formats. For more information about enabling this setting in Outlook 2002, see Microsoft Knowledge Base Article 307594. For information about this setting in Outlook Express 6, see Microsoft Knowledge Base Article 291387. Impact of Workaround: E-mail messages that are viewed in plain text format will not contain pictures, specialized fonts, animations, or other rich content. In addition: • The changes are applied to the preview pane and to open messages. • Pictures become attachments so that they are not lost. • Because the message is still in Rich Text or HTML format in the store, the object model (custom code solutions) may behave unexpectedly. Top of section FAQ for HTML Help Vulnerability - CAN-2004-0201: Top of section Top of section Top of section Security Update Information Installation Platforms and Prerequisites: For information about the specific security update for your platform, click the appropriate link: Windows Server 2003 (all versions) Windows XP (all versions) Windows 2000 (all versions) Windows NT 4.0 (all versions) Top of section Top of section Acknowledgments Microsoft thanks the following for working with us to help protect customers: • Brett Moore of Security-Assessment.com for reporting the HTML Help Vulnerability (CAN-2004-0201). Obtaining Other Security Updates: Updates for other security issues are available from the following locations: • Security updates are available from the Microsoft Download Center: You can find them most easily by doing a keyword search for "security_patch". • Updates for consumer platforms are available from the Windows Update Web site. Support: • Customers in the U.S. and Canada can receive technical support from Microsoft Product Support Services at 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates. • International customers can receive support from their local Microsoft subsidiaries. There is no charge for support that is associated with security updates. For more information about how to contact Microsoft for support issues, visit 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: For more information about the Windows Update Catalog, see Microsoft Knowledge Base Article 323166. • Office Update Software Update Services: By using Microsoft Software Update Services (SUS), administrators can quickly and reliably deploy the latest critical updates and security updates to Windows 2000 and Windows Server 2003-based servers, and to desktop systems that are running Windows 2000 Professional or Windows XP Professional. For more information about how to deploy this security update with Software Update Services, visit the Software Update Services Web site. Systems Management Server: Microsoft Systems Management Server (SMS) delivers a highly-configurable enterprise solution for managing updates. By using SMS, administrators can identify Windows-based systems that require security updates and to perform controlled deployment of these updates throughout the enterprise with minimal disruption to end users. For more information about how administrators can use SMS 2003 to deploy security updates, see the SMS 2003 Security Patch Management Web site. SMS 2.0 users can also use Software Updates Service Feature Pack to help deploy security updates. For information about SMS, visit the SMS Web site. Note SMS uses the Microsoft Baseline Security Analyzer and the Microsoft Office Detection Tool to provide broad support for security bulletin update detection and deployment. Some software updates may not be detected by these tools. Administrators can use the inventory capabilities of the SMS in these cases to target updates to specific systems. For more information about this procedure, see the following Web site. Some security updates require administrative rights following a restart of the system. Administrators can use the Elevated Rights Deployment Tool (available in the SMS 2003 Administration Feature Pack and in the SMS 2.0 Administration Feature Pack) to install these updates. 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 (July 13, 2004): Bulletin published [***** End Microsoft Security Bulletin MS04-023 *****] _______________________________________________________________________________ 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. 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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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