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From:MICROSOFT <secure_(at)_microsoft.com>
Date:12.12.2006
Subject:Microsoft Security Bulletin MS06-077 Vulnerability in Remote Installation Service Could Allow Remote Code Execution (926121)

Microsoft Security Bulletin MS06-077
Vulnerability in Remote Installation Service Could Allow Remote Code Execution (926121)
Published: December 12, 2006

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: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:


Microsoft Windows 2000 Service Pack 4 — Download the update

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.
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General Information

Executive Summary

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 Identifiers Impact of Vulnerability Windows 2000 Service Pack 4

RIS Writable Path Vulnerability - CVE-2006-5584


Remote 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.
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Frequently Asked Questions (FAQ) Related to This Security Update

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.
Product MBSA 1.2.1 EST MBSA 2.0

Microsoft Windows 2000 Service Pack 4


No


Yes


Yes

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.
Product SMS 2.0 SMS 2003

Microsoft Windows 2000 Service Pack 4


Yes


Yes

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.
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Vulnerability Details

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.
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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\Pa
rameters

4.


Add the DWORD 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.
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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.

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).

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.

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