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Microsoft Security Bulletin MS05-007 - Important

Vulnerability in Windows Could Allow Information Disclosure (888302)

Published: February 08, 2005

Version: 1.0

Issued: February 8, 2005
Version: 1.0

Summary

Who should read this document: Customers who use Microsoft Windows

Impact of Vulnerability: Information Disclosure

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:

Non-Affected Software:

  • Microsoft Windows 2000 Service Pack 3 and Microsoft Windows 2000 Service Pack 4
  • Microsoft Windows XP 64-Bit Edition Version 2003 (Itanium)
  • Microsoft Windows Server 2003
  • Microsoft Windows Server 2003 for Itanium-based Systems
  • Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and Microsoft Windows Millennium Edition (ME)

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, privately-reported vulnerability. The vulnerability is documented in the “Vulnerability Details” section of this bulletin.

An attacker who successfully exploited this vulnerability could remotely read the user names for users who have an open connection to an available shared resource.

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

Severity Ratings and Vulnerability Identifiers:

Vulnerability IdentifiersImpact of VulnerabilityWindows XP Service Pack 1Windows XP Service Pack 2
Named Pipe Vulnerability - CAN-2005-0051Information DisclosureImportantModerate

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.

I am still using Windows XP, but extended security update support ended on September 30th, 2004. What should I do?

The original version of Windows XP, generally known as Windows XP Gold or Windows XP Release to Manufacturing (RTM) version, reached the end of its extended security update support life cycle on September 30, 2004.

It should be a priority for customers who have this operating system version to migrate to supported operating system versions to prevent potential exposure to vulnerabilities. For more information about the Windows Service Pack Product Lifecycle, visit the Microsoft Support Lifecycle Web site. For more information about the Windows Product Lifecycle, visit the Microsoft Support Lifecycle Web site.

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.

Note After April 20, 2004, the Mssecure.xml file that is used by MBSA 1.1.1 and earlier versions is no longer being updated with new security bulletin data. Therefore, scans that are performed after that date by using MBSA 1.1.1 or earlier will be incomplete. All users should upgrade to MBSA 1.2 because it provides more accurate security update detection and supports additional products. Users can download MBSA 1.2.1 from the MBSA Web site. For more information about MBSA support, visit the following Microsoft Baseline Security Analyzer (MBSA) 1.2.1 Q&A 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

Named Pipe Vulnerability - CAN-2005-0051:

This is an information disclosure vulnerability. An attacker who successfully exploited this vulnerability could remotely read the user names for users who have an open connection to an available shared resource.

Mitigating Factors for Named Pipe Vulnerability - CAN-2005-0051:

  • 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.
  • Stopping or disabling the Computer Browser service and then restarting the affected system mitigates this vulnerability. The information disclosure does not happen if this service is stopped or disabled. By default, the Computer Browser service is not running on Windows XP Service Pack 2. Windows XP Service Pack 2 systems that are members of a domain have the Computer Browser disabled. By default, on Windows XP Service Pack 2 systems, that are not members of a domain, the Windows Firewall is enabled and the Computer Browser does not start. If the Windows Firewall is disabled or if File and Printer sharing is enabled, the Computer Browser service will start successfully and the system could be vulnerable to this issue.

Workarounds for Named Pipe Vulnerability - CAN-2005-0051:

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 the Computer Browser service

    Disabling the Computer Browser service and restarting the affected system will help protect from remote attempts to exploit this vulnerability.

    You can disable the Computer Browser service by following these steps:

    1. Click Start, and then click Control Panel (or point to Settings, and then click Control Panel).
    2. Double-click Administrative Tools.
    3. Double-click Services.
    4. Double-click Computer Browser Service.
    5. In the Startup type list, click Disabled.
    6. Click Stop, and then click OK.
    7. You must restart the affected system for this workaround to correction function.

    Impact of Workaround: If the Computer Browser service is disabled, any services that explicitly depend on the Computer Browser service may log an error message in the system event log. For more information about the Computer Browser service, see Microsoft Knowledge Base Article 188001.

  • Use the Group Policy settings to disable Computer Browser service on all affected systems that do not require this feature.
    Because the Computer Browser service is a possible attack vector, disable it by using the Group Policy settings. You can disable the startup of this service at the local, site, domain, or organizational unit level by using Group Policy object functionality in Windows 2000 domain environments or in Windows Server 2003 domain environments. For more information about how to disable this service through login scripts, see Microsoft Knowledge Base Article 297789

    Note You may also review the Windows 2000 Security Hardening Guide. This guide includes information about how to disable services.

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

    Impact of Workaround: If the Computer Browser service is disabled, any services that explicitly depend on the Computer Browser service may log an error message in the system event log. For more information about the Computer Browser service, see Microsoft Knowledge Base Article 188001.

  • Block TCP ports 139 and 445 at the firewall:

    These ports are used to initiate a connection with the affected protocol. Blocking them 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 the ports, visit the following Web site.

  • Use a personal firewall, such as the Internet Connection Firewall , which is included with Windows XP and do not enable “File and Printer Sharing for Microsoft Networks”.

    By default, the Internet Connection Firewall feature in Windows XP helps protect your Internet connection by blocking unsolicited incoming traffic. We recommend that you block all unsolicited incoming communication from the Internet. If you have enabled “File and Printer Sharing for Microsoft Networks” this option will create an exception to allow communication on the affected ports and would still allow a system to be vulnerable to this issue even with the Internet Connection Firewall enabled. The “File and Printer Sharing for Microsoft Networks” exception should be removed to help protect against this vulnerability.

    To enable the Internet Connection Firewall feature by using the Network Setup Wizard, follow these steps:

    1. Click Start, and then click Control Panel.
    2. In the default Category View, click Network and Internet Connections, and then click Setup or change your home or small office network. The Internet Connection Firewall feature is enabled when you select a configuration in the Network Setup Wizard that indicates that your system is connected directly to the Internet.

    To configure Internet Connection Firewall manually for a connection, follow these steps:

    1. Click Start, and then click Control Panel.
    2. In the default Category View, click Networking and Internet Connections, and then click Network Connections.
    3. Right-click the connection on which you want to enable Internet Connection Firewall, and then click Properties.
    4. Click to deselect “File and Printer Sharing for Microsoft Networks”.
    5. Click the Advanced tab.
    6. Click to select the Protect my computer or network by limiting or preventing access to this computer from the Internet check box, and then click OK.

    Note If you want to enable certain programs and services to communicate through the firewall, click Settings on the Advanced tab, and then select the programs, the protocols, and the services that are required.

  • 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. While this documentation references Windows 2000, it also applies to Windows XP.

  • 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. While this documentation references Windows 2000, it also applies to Windows XP.

FAQ for Named Pipe Vulnerability - CAN-2005-0051:

What is the scope of the vulnerability?
This is an information disclosure vulnerability. An attacker who successfully exploited this vulnerability could remotely read the user names of users who have an open connection to a shared resource. Note that this vulnerability would not allow an attacker to execute code or to elevate their user rights directly, but it could be used to produce useful information that could be used to try to further compromise the affected system.

What causes the vulnerability?
The process that is used by the affected software to validate authentication information when a client establishes an anonymous logon by using a named pipe connection.

What is a named pipe?
Named pipes can be used to provide communication between processes on the same computer or between processes on different computers across a network. Typical named pipe resources include file shares and print shares. For more information about named pipes, visit the following MSDN Library Web site.

How do I know if I use the Computer Browser service on my server?

By default, the Computer Browser service is installed and running on Windows XP Service Pack 1. By default, the Computer Browser service is disabled on Windows XP Service Pack 2. You can determine if the Computer Browser service is installed by following this procedure.

To verify the Computer Browser service:

  1. Click Start, click Programs, click Administrative Tools, and then click Services.
  2. Verify that the Computer Browser service is present.
  3. If the Computer Browser service is running, follow the instructions in the “Workarounds” section of this security bulletin to disable the service.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could remotely read the user names for users who have an open connection to an available shared resource.

Who could exploit the vulnerability?
Any anonymous user who could deliver a specially crafted request to the affected system could try to exploit this vulnerability.

What systems are primarily at risk from the vulnerability?
Windows XP is primarily at risk from this vulnerability. Other operating system versions perform additional validation on the communication request. This additional validation allows them to be able to successfully prevent anonymous connections. To perform this additional validation, they use registry settings such as RestrictAnonymous. This vulnerability allows communication with anonymous users on Windows XP even if the RestrictAnonymous registry setting is enabled. After you install the security update, the RestrictAnonymous registry setting on Windows XP will successfully block this kind of anonymous communication request. For more information about RestrictAnonymous, visit the following Microsoft Web site.

Could the vulnerability be exploited over the Internet?
Yes. An attacker could try to exploit this vulnerability over the Internet. Firewall best practices and standard default firewall configurations can help protect against attacks that originate from the Internet. Microsoft has provided information about how you can help protect your PC. End users can visit the Protect Your PC Web site. IT professionals can visit the Security Center Web site.

What does the update do?
The update removes the vulnerability by modifying the way that the process that is used by the affected software validates authentication information.

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 XP (all versions)

Prerequisites
This security update requires Microsoft Windows XP Service Pack 1 or a later version. For more information, see Microsoft Knowledge Base Article 322389.

Inclusion in Future Service Packs:
The update for this issue will be included in a future Service Pack or Update Rollup.

Installation Information

This security update supports the following setup switches:

/help                 Displays the command-line options

Setup Modes

/quiet                Quiet mode (no user interaction or display)

/passive            Unattended mode (progress bar only)

      /uninstall          Uninstalls the package

Restart Options

/norestart          Do not restart when installation has completed

/forcerestart      Restart after installation

Special Options

/l                        Lists installed Windows hotfixes or update packages

/o                       Overwrite OEM files without prompting

/n                       Do not backup files needed for uninstall

/f                        Force other programs to close when the computer shuts down

/integrate:path  Integrates the update into the Windows source files located at the path specified

/extract             Extracts files without starting the Setup program

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.

Deployment Information

To install the security update without any user intervention, use the following command at a command prompt for Microsoft Windows XP:

Windowsxp-kb888302-x86-enu /passive /quiet

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

Windowsxp-kb888302-x86-enu /norestart

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

Restart Requirement

This update does not require a restart. The installer stops the required services, applies the update, and then restarts the services. However, if the required services cannot be stopped for any reason, or if required files are being used, this update will require a restart. If this behavior occurs, a message appears that advises you to restart. To help reduce the chance that a reboot will not be required, stop all affected services and close all applications that may use the affected files prior to installing the security update.

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%\$NTUninstallKB888302$\Spuninst folder. The Spuninst.exe utility supports the following setup switches:

/help                 Displays the command line options

Setup Modes

/quiet                Quiet mode (no user interaction or display)

/passive            Unattended mode (progress bar only)

Restart Options

/norestart          Do not restart when installation is complete

/forcerestart      Restart after installation

Special Options

/f                        Force other programs to close when the computer shuts down

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 XP Home Edition Service Pack 1, Windows XP Professional Service Pack 1, Windows XP Tablet PC Edition, Windows XP Media Center Edition, Windows XP Home Edition Service Pack 2, Windows XP Professional Service Pack 2, Windows XP Tablet PC Edition 2005, and Windows XP Media Center Edition 2005:

File NameVersionDateTimeSizeFolder
Srvsvc.dll5.1.2600.161307-Dec-200419:3479,872SP1QFE
Srvsvc.dll5.1.2600.257707-Dec-200419:3296,768SP2GDR
Srvsvc.dll5.1.2600.257707-Dec-200419:2996,768SP2QFE

Windows XP 64-Bit Edition Service Pack 1 (Itanium):

File NameVersionDateTimeSizeCPU
Srvsvc.dll5.1.2600.161307-Dec-200419:34207,872IA-64

Notes The Windows XP version of this security update is packaged as a dual-mode package. Dual-mode packages contain files for the original version of Windows XP Service Pack 1 (SP1) and files for Windows XP Service Pack 2 (SP2).

For more information about dual-mode packages, see Microsoft Knowledge Base Article 328848.

When you install this security update on Windows XP SP2, the installer checks to see if one or more of the files that are being updated on your system have previously been updated by a Microsoft hotfix.

If you have previously installed a hotfix to update an affected file, one of the following conditions occurs, depending on your operating system:

  • Windows XP SP2

    The installer copies the SP2QFE files to your system.

If you have not previously installed a hotfix to update an affected file, one of the following conditions occurs, depending on your operating system:

  • Windows XP SP2

    The installer copies the SP2GDR files to your system.

For more information about this behavior, see Microsoft Knowledge Base Article 824994.

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.

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 keys.

    For Windows XP Home Edition Service Pack 1, Windows XP Professional Service Pack 1, Windows XP Tablet PC Edition, Windows XP Media Center Edition, Windows XP Home Edition Service Pack 2, Windows XP Professional Service Pack 2, Windows XP Tablet PC Edition 2005, and Windows XP Media Center Edition 2005:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\Windows XP\SP3\KB888302\Filelist

    Note These registry keys may not contain a complete list of installed files. Also, these registry keys may not be created correctly if an administrator or an OEM integrates or slipstreams the 888302 security update into the Windows installation source files.

Other Information

Acknowledgments

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

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 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, 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 (February 8, 2005): Bulletin published

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