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Microsoft Security Bulletin MS05-024 - Important

Vulnerability in Web View Could Allow Remote Code Execution (894320)

Published: May 10, 2005

Version: 1.0

Summary

Who should read this document: Customers who use Microsoft Windows

Impact of Vulnerability: Remote Code Execution

Maximum Severity Rating: Important

Recommendation: Customers should apply the update at the earliest opportunity.

Security Update Replacement: None

Caveats: None

Tested Software and Security Update Download Locations:

Affected Software:

  • Microsoft Windows 2000 Service Pack 3 and Microsoft Windows 2000 Service Pack 4 – 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 XP Service Pack 1 and Microsoft Windows XP Service Pack 2
  • Microsoft Windows XP 64-Bit Edition Service Pack 1 (Itanium)
  • Microsoft Windows XP 64-Bit Edition Version 2003 (Itanium)
  • Microsoft Windows XP Professional x64 Edition
  • Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service Pack 1
  • Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft Windows Server 2003 with SP1 for Itanium-based Systems
  • Microsoft Windows Server 2003 x64 Edition

The software in this list has been tested to determine whether the versions are affected. Other versions either no longer include security update support or may not be affected. To determine the support life cycle for your product and version, visit the Microsoft Support Lifecycle Web site.

General Information

Executive Summary:

This update resolves a newly-discovered, public vulnerability. A remote code execution vulnerability exists in the way that Web View in Windows Explorer handles certain HTML characters in preview fields. By persuading a user to preview a malicious file, an attacker could execute arbitrary code in the context of the logged on user. The vulnerability is documented in the “Vulnerability Details” section of this bulletin.

If a user is logged on with administrative user rights, 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 user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. However, user interaction is required to exploit this vulnerability.

We recommend that customers apply the update at the earliest opportunity.

Severity Ratings and Vulnerability Identifiers:

Vulnerability IdentifiersImpact of VulnerabilityWindows 98, 98 SE, MEWindows 2000
Web View Script Injection Vulnerability - CAN-2005-1191Remote Code ExecutionNot CriticalImportant

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.

How does the extended support for Windows 98, Windows 98 Second Edition, and Windows Millennium Edition affect the release of security updates for these operating systems?
Microsoft will only release security updates for critical security issues. Non-critical security issues are not offered during this support period. For more information about the Microsoft Support Lifecycle policies for these operating systems, visit the following Web site.

For more information about severity ratings, visit the following Web site.

Are Windows 98, Windows 98 Second Edition, or Windows Millennium Edition critically affected by one or more of the vulnerabilities that are addressed in this security bulletin?
No. Although Windows Millennium Edition does contain the affected component, the vulnerability is not critical. For more information about severity ratings, visit the following Web site.

Extended security update support for Microsoft Windows NT Workstation 4.0 Service Pack 6a and Windows 2000 Service Pack 2 ended on June 30, 2004. Extended security update support for Microsoft Windows NT Server 4.0 Service Pack 6a ended on December 31, 2004. I’m still using one of these operating systems, what should I do?

Windows NT Workstation 4.0 Service Pack 6a, Windows NT Server 4.0 Service Pack 6a, and Windows 2000 Service Pack 2 have reached the end of their life cycles. It should be a priority for customers who have these operating system versions to migrate to supported versions to prevent potential exposure to vulnerabilities. For more information about the Windows Product Lifecycle, visit the following Microsoft Support Lifecycle Web site. For more information about the extended security update support period for these operating system versions, visit the Microsoft Product Support Services Web site.

Customers who require additional support for Windows NT 4.0 SP6a must contact their Microsoft account team representative, their Technical Account Manager, or the appropriate Microsoft partner representative for custom support options. Customers without an Alliance, Premier, or Authorized Contract can contact their local Microsoft sales office. For contact information, visit the Microsoft Worldwide Information Web site, select the country, and then click Go to see a list of telephone numbers. When you call, ask to speak with the local Premier Support sales manager.

For more information, see the Windows Operating System Product Support Lifecycle FAQ.

Can I use the Microsoft Baseline Security Analyzer (MBSA) to determine whether this update is required?
Yes. MBSA will determine whether this update is required. For more information about MBSA, visit the MBSA Web site.

Can I use Systems Management Server (SMS) to determine whether this update is required?
Yes. SMS can help detect and deploy this security update. For information about SMS, visit the SMS Web site

The Security Update Inventory Tool is required for detecting Microsoft Windows and other affected Microsoft products. For more information about the limitations of the Security Update Inventory Tool, see Microsoft Knowledge Base Article 306460

For more information about SMS, visit the SMS Web site.

Web View Script Injection Vulnerability - CAN-2005-1191:

A remote code execution vulnerability exists in the way that Web View in Windows Explorer handles certain HTML characters in preview fields. By persuading a user to preview a malicious file, an attacker could execute code. However, user interaction is required to exploit this vulnerability.

Mitigating Factors for Web View Script Injection Vulnerability - CAN-2005-1191:

  • 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 Web site. After they click the link, they would be prompted to perform an action. An attack could only occur after they performed these actions.
  • An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
  • The vulnerability could not be exploited automatically through e-mail. For an attack to be successful through email a user must save an attachment locally and preview from within Windows Explorer.

Workarounds for Web View Script Injection Vulnerability - CAN-2005-1191:

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 in the following section.

  • Disable Web View:

    Disabling Web View will reduce the ability to maliciously use this feature to perform an attack. To disable Web View, follow these steps:

    1. Open My Computer
    2. Under the Tools menu, select Folder Options.
    3. On the General tab in the Web View section, select Use Windows classic folders
    4. Click OK
    5. These settings will only fully take affect after a user has logged off and then logged back onto the affected system.

    Impact of Workaround: This change will reduce the functionality of Windows Explorer by removing the left hand task pane which contains links to common folders and tasks.

  • Use the Group Policy settings to disable Web View on all affected systems that do not require this feature.

    Disabling Web View will reduce the ability to maliciously use this feature to perform an attack.

    For more information about Group Policy, visit the following Web sites:

    Impact of Workaround: This change will reduce the functionality of Windows Explorer by removing the left hand task pane which contains links to common folders and tasks.

  • Block Outbound TCP ports 139 and 445 at the perimeter firewall:

    These ports are used to initiate a connection via the Server Message Block (SMB) protocol. Blocking outbound SMB traffic at the perimeter firewall will help prevent systems from attempting to connect to a malicious file server outside of the firewall. For more information about the ports, visit the following web site.

    Impact of Workaround: Machines behind the firewall will be unable to access trusted file servers via the Server Message Block (SMB) protocol outside of the network.

FAQ for Web View Script Injection Vulnerability - CAN-2005-1191:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in the way that Web View within Windows Explorer handles certain HTML characters in preview fields. By persuading a user to preview a malicious file, an attacker could execute code.

If a user is logged on with administrative user rights, 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 user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. However, user interaction is required to exploit this vulnerability.

What causes the vulnerability?
The process used by Windows Explorer when in Web View to validate HTML characters in certain document fields.

What is Web View?
Web View is one of two different formats provided by Windows Explorer for viewing file and folder information. This feature allows users to preview documents in a thumbnail view before opening. In addition, information such as title and author is displayed.

What is SMB?
Server Message Block (SMB), and its follow-on, Common Internet File System (CIFS), is the Internet Standard protocol that Windows uses to share files, printers, serial ports, and also to communicate between computers. To do this, SMB uses named pipes and mail slots. In a networked environment, servers make file systems and resources available to clients. Clients make SMB requests for resources. Servers make SMB responses. This is described as a client server, request-response protocol.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take complete control of the affected system.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by creating a malicious file and placing it in a location either locally or remotely. The attacker would then need to persuade a user to connect to the folder within Windows Explorer and preview the document. The document could then cause the affected system to execute code. Additionally, an attacker could persuade a user to save a file from an email message to a local storage device. As in the previous scenario, the attacker would then need to persuade the user to connect to the folder with Windows Explorer and preview the document.

What systems are primarily at risk from the vulnerability?
Workstations and terminal servers are primarily at risk. Servers could be at more risk if users who do not have sufficient administrative permissions are given the ability to log on to servers and to run programs. However, best practices strongly discourage allowing this.

Are Windows 98, Windows 98 Second Edition or Windows Millennium Edition critically affected by this vulnerability?
No. Although Windows Millennium Edition does contain the affected component, the vulnerability is not critical. For more information about severity ratings, visit the following Web site.

What does the update do?
The update addresses the vulnerability by modifying the way that Windows Explorer validates HTML characters in certain document fields.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
Yes. This vulnerability has been publicly disclosed. It has been assigned Common Vulnerability and Exposure number CAN-2005-1191.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers, however examples of proof of concept code had been published when this security bulletin was originally issued.

Does applying this security update help protect customers from the code that has been published publicly that attempts to exploit this vulnerability?
Yes. This security update addresses the vulnerability for which proof of concept code has been published.

Affected Software:

For information about the specific security update for your affected software, click the appropriate link:

Windows 2000 (all versions)

Prerequisites
For Windows 2000, this security update requires Service Pack 3 (SP3) or Service Pack 4 (SP4). For Small Business Server 2000, this security update requires Small Business Server 2000 Service Pack 1a (SP1a) or Small Business Server 2000 running with Windows 2000 Server Service Pack 4 (SP4).

The software that is listed has been tested to determine whether the versions are affected. Other versions either no longer include security update support or may not be affected. To determine the support life cycle for your product and version, visit the Microsoft Support Lifecycle Web site.

For more information about how to obtain the latest service pack, see Microsoft Knowledge Base Article 260910.

Inclusion in Future Service Packs:
There are no additional Windows 2000 Service Packs planned at this time.

Installation Information

This security update supports the following setup switches.

Supported Security Update Installation Switches
SwitchDescription
/help Displays the command-line options
Setup Modes
/passive Unattended Setup mode. No user interaction is required, but installation status is displayed. If a restart is required at the end of Setup, a dialog box will be presented to the user with a timer warning that the computer will restart in 30 seconds.
/quiet Quiet mode. This is the same as unattended mode, but no status or error messages are displayed.
Restart Options
/norestart Does not restart when installation has completed
/forcerestart Restarts the computer after installation and force other applications to close at shutdown without saving open files first.
/warnrestart[:x] Presents a dialog box with a timer warning the user that the computer will restart in x seconds. (The default setting is 30 seconds.) Intended for use with the /quiet switch or the /passive switches.
/promptrestart Display a dialog box prompting the local user to allow a restart
Special Options
/overwriteoem Overwrites OEM files without prompting
/nobackup Does not backup files needed for uninstall
/forceappsclose Forces other programs to close when the computer shuts down
/log:path Allows the redirection of installation log files
/integrate:path Integrates the update into the Windows source files. These files are located at the path that is specified in the switch.
/extract[:path] Extracts files without starting the Setup program
/ER Enables extended error reporting
/verbose Enables verbose logging. During installation, creates %Windir%\CabBuild.log. This log details the files that are copied. Using this switch may cause the installation to proceed more slowly.

Note You can combine these switches into one command. For backward compatibility, the security update also supports the setup switches that the earlier version of the Setup program uses. For more information about the supported installation switches, see Microsoft Knowledge Base Article 262841. For more information about the Update.exe installer, visit the Microsoft TechNet Web site. For more information about the terminology that appears in this bulletin, such as hotfix, see Microsoft Knowledge Base Article 824684.

Deployment Information

To install the security update without any user intervention, use the following command at a command prompt for Windows 2000 Service Pack 3 and Windows 2000 Service Pack 4:

Windows2000-kb894320-x86-enu /quiet

To install the security update without forcing the system to restart, use the following command at a command prompt for Windows 2000 Service Pack 3 and Windows 2000 Service Pack 4:

Windows2000-kb894320-x86-enu /norestart

For more information about how to deploy this security update with Software Update Services, visit the Software Update Services Web site.

Restart Requirement

You must restart your system after you apply this security update. For more information about the reasons why you may be prompted to restart your computer, see Microsoft Knowledge Base Article 887012.

Removal Information

To remove this security update, use the Add or Remove Programs tool in Control Panel.

System administrators can also use the Spuninst.exe utility to remove this security update. The Spuninst.exe utility is located in the %Windir%\$NTUninstallKB894320$\Spuninst folder.

Supported Spuninst.exe Switches
SwitchDescription
/help Displays the command-line options
Setup Modes
/passive Unattended Setup mode. No user interaction is required, but installation status is displayed. If a restart is required at the end of Setup, a dialog box will be presented to the user with a timer warning that the computer will restart in 30 seconds.
/quiet Quiet mode. This is the same as unattended mode, but no status or error messages are displayed.
Restart Options
/norestart Does not restart when installation has completed
/forcerestart Restarts the computer after installation and force other applications to close at shutdown without saving open files first.
/warnrestart[:x] Presents a dialog box with a timer warning the user that the computer will restart in x seconds. (The default setting is 30 seconds.) Intended for use with the /quiet switch or the /passive switches.
/promptrestart Display a dialog box prompting the local user to allow a restart
Special Options
/forceappsclose Forces other programs to close when the computer shuts down
/log:path Allows the redirection of installation log files

File Information

The English version of this security update has the file attributes that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

Windows 2000 Service Pack 3, Windows 2000 Service Pack 4, and Small Business Server 2000:

File NameVersionDateTimeSize
Webvw.dll5.0.3900.703629-Apr-200507:161,119,504
Updspapi.dll6.1.22.425-Feb-200517:43371,936

Verifying that the Update Has Been Applied

  • Microsoft Baseline Security Analyzer

    To verify that a security update has been applied to an affected system, you may be able to use the Microsoft Baseline Security Analyzer (MBSA) tool. MBSA allows administrators to scan local and remote systems for missing security updates and for common security misconfigurations. For more information about MBSA, visit the Microsoft Baseline Security Analyzer Web site.

  • File Version Verification

    Note Because there are several versions of Microsoft Windows, the following steps may be different on your computer. If they are, see your product documentation to complete these steps.

    1. Click Start, and then click Search.
    2. In the Search Results pane, click All files and folders under Search Companion.
    3. In the All or part of the file name box, type a file name from the appropriate file information table, and then click Search.
    4. In the list of files, right-click a file name from the appropriate file information table, and then click Properties.

      Note Depending on the version of the operating system or programs installed, some of the files that are listed in the file information table may not be installed.
    5. On the Version tab, determine the version of the file that is installed on your computer by comparing it to the version that is documented in the appropriate file information table.

      Note Attributes other than the file version may change during installation. Comparing other file attributes to the information in the file information table is not a supported method of verifying that the update has been applied. Also, in certain cases, files may be renamed during installation. If the file or version information is not present, use one of the other available methods to verify update installation.
  • Registry Key Verification

    You may also be able to verify the files that this security update has installed by reviewing the following registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\Windows 2000\SP5\KB894320\Filelist

    Note This registry key may not contain a complete list of installed files. Also, this registry key may not be created correctly when an administrator or an OEM integrates or slipstreams the 894320 security update into the Windows installation source files.

Other Information

Obtaining Other Security Updates:

Updates for other security issues are available at the following locations:

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:

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 by using 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 can 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, visit 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 Analyze, Microsoft Office Detection Tool, and the Enterprise Update Scanning 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, visit 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 (May 10, 2005): Bulletin published

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