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Microsoft Security Bulletin MS06-077 - Important

Vulnerability in Remote Installation Service Could Allow Remote Code Execution (926121)

Published: December 12, 2006 | Updated: March 21, 2007

Version: 1.1

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: Microsoft Knowledge Base Article 926121 documents the currently known issues that customers may experience when they install this security update. The article also documents recommended solutions for these issues. For more information, see Microsoft Knowledge Base Article 926121.

Tested Software and Security Update Download Locations:

Affected Software:

Non-Affected Software:

  • Microsoft Windows XP Service Pack 2
  • 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
  • Windows Vista

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 privately reported vulnerability. The vulnerability is documented in the "Vulnerability Details" section of this bulletin.

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.

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

Severity Ratings and Vulnerability Identifiers:

Vulnerability IdentifiersImpact of VulnerabilityWindows 2000 Service Pack 4
RIS Writable Path Vulnerability - CVE-2006-5584Remote Code Execution
Important
  • 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.

Extended security update support for Microsoft Windows 98, Windows 98 Second Edition, or Windows Millennium Edition ended on July 11, 2006. I am still using one of these operating systems; what should I do? 
Windows 98, Windows 98 Second Edition, and Windows Millennium Edition have reached the end of their support 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.

Extended security update support for Microsoft Windows XP Home Edition Service Pack 1 or Service Pack 1a, Windows XP Media Center Edition 2002 Service Pack 1, Windows XP Media Center Edition 2004 Service Pack 1, Windows XP Professional Service Pack 1 or Service Pack 1a, and Windows XP Tablet PC Edition Service Pack 1 ended on October 10, 2006. I am still using one of these operating systems; what should I do?
Windows XP (all versions) Service Pack 1has reached the end of its support life cycle. 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.

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. Extended security update support for Microsoft Windows 2000 Service Pack 3 ended on June 30, 2005. I am 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, Windows 2000 Service Pack 2, and Windows 2000 Service Pack 3 have reached the end of their support 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 custom support for these products 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.

For more information, visit the Windows Operating System FAQ.

Can I use the Microsoft Baseline Security Analyzer (MBSA) to determine whether this update is required?
The following table provides the MBSA detection summary for this security update.

ProductMBSA 1.2.1ESTMBSA 2.0
Microsoft Windows 2000 Service Pack 4NoYesYes

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

For more information about the programs that Microsoft Update and MBSA 2.0 currently do not detect, see Microsoft Knowledge Base Article 895660.

For more detailed information, see Microsoft Knowledge Base Article 910723.

What is the Enterprise Update Scan Tool (EST)?
As part of an ongoing commitment to provide detection tools for bulletin-class security updates, Microsoft delivers a stand-alone detection tool whenever the Microsoft Baseline Security Analyzer (MBSA) and the Office Detection Tool (ODT) cannot detect whether the update is required for an MSRC release cycle. This stand-alone tool is called the Enterprise Update Scan Tool (EST) and is designed for enterprise administrators. When a version of the Enterprise Update Scan Tool is created for a specific bulletin, customers can run the tool from a command-line interface (CLI) and view the results of the XML output file. To help customers better utilize the tool, detailed documentation will be provided with the tool. There is also a version of the tool that offers an integrated experience for SMS administrators.

Can I use a version of the Enterprise Update Scan Tool (EST) to determine whether this update is required?
Yes. Microsoft has created a version of EST that will determine if you have to apply this update. For download links and more information about the version of EST that is being released this month, see Microsoft Knowledge Base Article 894193. SMS customers should review the following FAQ, “Can I use Systems Management Server (SMS) to determine whether this update is required?" for more information about SMS and EST.

Can I use Systems Management Server (SMS) to determine whether this update is required?
The following table provides the SMS detection summary for this security update.

ProductSMS 2.0SMS 2003
Microsoft Windows 2000 Service Pack 4YesYes

SMS 2.0 and SMS 2003 Software Update Services (SUS) Feature Pack can use MBSA 1.2.1 for detection and therefore have the same limitation that is listed earlier in this bulletin related to programs that MBSA 1.2.1 does not detect.

For SMS 2.0, the SMS SUS Feature Pack, which includes the Security Update Inventory Tool (SUIT), can be used by SMS to detect security updates. SMS SUIT uses the MBSA 1.2.1 engine for detection. For more information about SUIT, visit the following Microsoft Web site. For more information about the limitations of SUIT, see Microsoft Knowledge Base Article 306460. The SMS SUS Feature Pack also includes the Microsoft Office Inventory Tool to detect required updates for Microsoft Office applications.

For SMS 2003, the SMS 2003 Inventory Tool for Microsoft Updates (ITMU) can be used by SMS to detect security updates that are offered by Microsoft Update and that are supported by Windows Server Update Services. For more information about the SMS 2003 ITMU, visit the following Microsoft Web site. SMS 2003 can also use the Microsoft Office Inventory Tool to detect required updates for Microsoft Office applications.

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

For more detailed information, see Microsoft Knowledge Base Article 910723.

RIS Writable Path Vulnerability - CVE-2006-5584:

The Remote Installation Service enables a TFTP service on the server which by default could allow an anonymous user to potentially overwrite existing operating system files or upload a specially crafted file. This could allow an attacker to compromise operating system installs offered by the RIS server.

Mitigating Factors for RIS Writable Path Vulnerability - CVE-2006-5584:

  • The attacker must be able to TFTP to the Remote Installation Server to place a specially crafted file or program.
  • The Remote Install Service is not installed by default on Windows 2000 Service Pack 4.
  • For customers who require the affected component, firewall best practices and standard default firewall configurations can help protect networks from attacks that originate outside the enterprise perimeter. Best practices recommend that systems that are connected to the Internet have a minimal number of ports exposed.

Workarounds for RIS Writable Path Vulnerability - CVE-2006-5584:

Microsoft has tested the following workarounds. Although 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.

  • Configure the TFTP service as read only.

    You can configure the TFTP service as read only by setting a value in the registry.

    Note Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in regedit.exe.

    Note We recommend backing up the registry before you edit it.

    To prevent the RIS server from accepting unauthorized access, add the following to the registry using Regedit.exe.

    1. Click Start, and click Run, type “regedit” (without the quotation marks), and the click OK.
    2. In Registry Editor, create the following registry key:
    3. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TFTPD\Parameters
    4. Add the REG_SZ Value: Masters. Set the value to 0. This value disables writable TFTPD access.
    5. You must restart the TFTP service for this change to take effect
    6. TP service:
    7. Click Start, click Run, type Run type “cmd” (without the quotation marks), and then click OK.
    8. In the cmd Window type “Net stop TFTPD” (without the quotation marks) and press Enter.
  • Block port 69 (UDP) at the firewall.

    This port is used to initiate a connection with the affected component. Blocking UDP port 69 at the firewall will help protect systems that are behind that firewall from attempts to exploit this vulnerability. We recommend that you block all unsolicited inbound communication from the Internet to help prevent attacks that may use other ports. For more information about ports, visit the following Web site.

  • Stop the TFTP service if it is not needed
    1. Click Start, click Run, type “cmd” (without the quotation marks), and then click OK.
    2. In the cmd Window type “Net stop TFTPD” (without the quotation marks) and press Enter.

    Impact of Workaround: If you disable the TFTP service, users will not be able to upload, view or write to the contents of TFTP directories.

  • To help protect from network-based attempts to exploit this vulnerability, enable advanced TCP/IP filtering on systems that support this feature.

    You can enable advanced TCP/IP filtering to block all unsolicited inbound traffic. For more information about how to configure TCP/IP filtering, see Microsoft Knowledge Base Article 309798.

  • To help protect from network-based attempts to exploit this vulnerability, block the affected ports by using IPSec on the affected systems.

    Use Internet Protocol security (IPSec) to help protect network communications. Detailed information about IPSec and about how to apply filters is available in Microsoft Knowledge Base Article 313190 and Microsoft Knowledge Base Article 813878.

FAQ for RIS Writable Path Vulnerability - CVE-2006-5584:

What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely 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.

What causes the vulnerability?
The vulnerability is caused by allowing anonymous access to the file structure of a hosted operating system build through the RIS TFTP service.

What is RIS?
Remote Installation Services (RIS) is a Pre-boot Execution Environment (PXE)-based deployment technology that allows Windows setup to initiate over a network.

Who could exploit the vulnerability?
Any anonymous user who could deliver a specially crafted executable or file to the affected RIS system could try to exploit this vulnerability at a later time on systems that are built using the tampered operating system build.

What systems are primarily at risk from the vulnerability?
All Windows 2000 Server Service Pack 4 systems that have RIS installed are primarily at risk from this vulnerability.

Could the vulnerability be exploited over the Internet?
Yes. An attacker could try to exploit this vulnerability over the Internet, but they must first have network permissions to gain access to the RIS service. Firewall best practices and standard default firewall configurations can help protect against attacks that originate from the Internet.

What does the update do?
The update removes the vulnerability by not allowing anonymous TFTP users the ability to write to the RIS hosted operating system build’s file structure. The update adds the registry key identified in the Workarounds section of the bulletin.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure. Microsoft had not received any information to indicate that this vulnerability had been publicly disclosed when this security bulletin was originally issued.

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 and had not seen any examples of proof of concept code published when this security bulletin was originally issued.

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 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
The update for this issue may be included in a future Update Rollup.

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 forces other applications to close at shutdown without saving open files first.
/warnrestart[:x] Displays 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 switch.
/promptrestart Display a dialog box prompting the local user to allow a restart.
Special Options
/overwriteoem Overwrites OEM files without prompting.
/nobackup Does not back up files needed for uninstallation.
/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 4:

Windows2000-kb926121-x86-enu /quiet

Note Use of the /quiet switch will suppress all messages. This includes suppressing failure messages. Administrators should use one of the supported methods to verify the installation was successful when they use the /quiet switch. Administrators should also review the KB926121.log file for any failure messages when they use this switch.

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

Windows2000-kb926121-x86-enu /norestart

For more information about how to deploy this security update with Software Update Services, visit the Software Update Services Web site. For more information about how to deploy this security update using Windows Server Update Services, visit the Windows Server Update Services Web site. This security update will also be available through the Microsoft Update Web site.

Restart Requirement

This update requires a restart.

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%\$NTUninstallKB926121$\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 forces other applications to close at shutdown without saving open files first.
/warnrestart[:x] Displays 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 switch.
/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

As this update is only modifying system properties for the identified services, no new binaries are applied to the system as a result of the update installation.

For more information about the terminology that appears in this bulletin, such as hotfix, see Microsoft Knowledge Base Article 824684.

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 can 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.

  • 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\KB926121\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 security update into the Windows installation source files.

Other Information

Acknowledgments

Microsoft thanks the following for working with us to help protect customers:

  • Nicolas Ruff for reporting the RIS Writable Path TFTP Vulnerability (CVE-2006-5584).

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 security updates by using Software Update Services, visit the Software Update Services Web site.

Windows Server Update Services:

By using Windows Server Update Services (WSUS), administrators can quickly and reliably deploy the latest critical updates and security updates for Windows 2000 operating systems and later, Office XP and later, Exchange Server 2003, and SQL Server 2000 onto Windows 2000 and later operating systems.

For more information about how to deploy security updates using Windows Server Update Services, visit the Windows Server 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 Analyzer, the Microsoft Office Detection Tool, and the Enterprise Update Scan 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 (December 12, 2006): Bulletin published.
  • V1.1 (March 21, 2007): Bulletin revised. Workaround Section updated to reflect the correct registry key value. The correct registry key value type is REG_SZ and not REG_DWORD as previously listed.

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