Microsoft Security Bulletin MS04-021

Microsoft Security Bulletin MS04-021
Security Update for IIS 4.0 (841373)

Issued: July 13, 2004
Version: 1.0

Summary
Who should read this document: Customers who use Microsoft® Windows® NT® 4.0

Impact of Vulnerability: Remote Code Execution

Maximum Severity Rating: Important

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

Security Update Replacement: None

Caveats: None

Tested Software and Security Update Download Locations:

Affected Software:

• Microsoft Windows NT® Workstation 4.0 Service Pack 6a – Download the update

• Microsoft Windows NT Server 4.0 Service Pack 6a – Download the update

Non-Affected Software:

• Microsoft Windows 2000 Service Pack 2, Microsoft Windows 2000 Service Pack 3, Microsoft Windows 2000 Service Pack 4

• Microsoft Windows XP and Microsoft Windows XP Service Pack 1

• Microsoft Windows XP 64-Bit Edition Service Pack 1

• Microsoft Windows XP 64-Bit Edition Version 2003

• Microsoft Windows Server™ 2003

• Microsoft Windows Server 2003 64-Bit Edition

• Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and Microsoft Windows Millennium Edition (Me)

Tested Microsoft Windows Components:

Affected Components:

• Microsoft Internet Information Server (IIS) 4.0

Non-Affected Components:

• Microsoft Internet Information Services 5.0 (included with Windows 2000 Server)

• Microsoft Internet Information Services 5.1 (included with Windows XP)

• Microsoft Internet Information Services 6.0 (included with Windows Server 2003

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

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General Information
Executive Summary

Executive Summary:

This update resolves a newly-discovered, privately reported vulnerability.

An attacker who successfully exploited this vulnerability could take complete control of an affected system, including installing programs; viewing, changing, or deleting data; or creating new accounts that have full privileges.

Customers should install the update at the earliest opportunity.

Severity Ratings and Vulnerability Identifiers:

Vulnerability Identifiers Impact of Vulnerability Windows NT 4.0
IIS Redirection Vulnerability - CAN-2004-0205
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

I'm still using Microsoft Windows NT 4.0 Workstation Service Pack 6a, but extended security update support ended on June 30, 2004. However, this bulletin has a security update for this operating system. Why is that?
Windows NT 4.0 Workstation Service Pack 6a has reached the end of its life cycles as previously documented, and Microsoft extended this support to June 30, 2004. However, the end-of-life for the extended support period occurred very recently. In this case, the majority of the steps that are required to address this vulnerability were completed before June 30, 2004. Therefore, we have been able to release security updates for these operating system versions as part of this security bulletin. We do not anticipate doing this for future vulnerabilities affecting these operating system versions.

It should be a priority for customers who have these operating system versions to migrate to supported versions to prevent potential exposure to future vulnerabilities. For more information about the Windows Product Life Cycle, 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 following Microsoft Product Support Services Web site.

Customers who require additional support for Windows NT Workstation 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 phone numbers. When you call, ask to speak with the local Premier Support sales manager.

For more information, see the Windows Operating System FAQ.

Can I use the Microsoft Baseline Security Analyzer (MBSA) to determine if this update is required?
Yes. MBSA will determine if 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 with 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 from the MBSA Web site. For more information about MBSA support, visit the following Microsoft Baseline Security Analyzer 1.2 Q&A Web site.

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

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Vulnerability Details

IIS Redirection Vulnerability - CAN-2004-0205:

A buffer overrun vulnerability exists in Internet Information Server 4.0 that could allow remote code execution on an affected system. An attacker who successfully exploited this vulnerability could take complete control of the affected system.

Mitigating Factors for IIS Redirection Vulnerability - CAN-2004-0205:

• Internet Information Server 5.0, Internet Information Server 5.1, and Internet Information Server 6.0 are not affected by this vulnerability.

• Customers who have disabled permanent redirects are not at risk from this vulnerability.

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Workarounds for IIS Redirection Vulnerability - CAN-2004-0205:

Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified below.

• Disable permanent redirects

Open the IIS Configuration manager.

Right-click the Web site that you want to administer, and then click Properties.

Click Home Directory.

Uncheck A permanent redirection for this resource, and then click OK.

Impact of Workaround: The server will no longer perform redirects.

• Use URLScan to disallow the use of large requests

Visit the following Web site to Download and install the URLScan security tool.

Start Notepad, and then open the %systemroot%\winnt\urlscan\UrlScan.ini file.

Configure the MaxUrl setting so that it limits requests to 16 kilobytes (KB). To configure the MaxUrl setting to that it limits requests to 16 KB, add the following line to the RequestLimits section of the file:

MaxUrl = 16384

Save, and then close the UrlsScan.ini file.

Start, and then stop the World Wide Web Publishing Service by using the Services item in Control Panel. You can also do this by using the net stop IIsadmin command and the net start w3svc command at a command prompt. For information about how to do this, see Microsoft Knowledge Base Article 185382

Impact of workaround: The URLScan tool will block all the incoming requests that are larger than 16 KB.

• Reduce MaxClientRequestBuffer

Start Registry Editor (Regedt32.exe).

Locate the following key in the registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\w3svc\parameters

Click Edit, click Add Value, and then add the following registry value:

• Value Name: MaxClientRequestBufferData Type: REG_DWORD

In the DWORD Editor dialog box, under Radix, click Decimal.

In the Data box, type the number of bytes for the maximum URL request. Set the size so that it is equal to or less than 16384 bytes.

Note You must restart the IIS service for the changes to take effect.

For more information, see Microsoft Knowledge Base Article 260694

Impact of workaround: Any incoming request that is larger than 16384 bytes will fail.

• Stop, disable, or remove IIS

• You can stop the World Wide Web Publishing Service component of IIS by issuing the net stop w3svc command at a command prompt.

• You can use the IIS Manager to disable or stop IIS.

• You can stop or disable the World Wide Web Publishing Service by using the Services item in Control Panel.

• You can use Add or Remove Programs in Control Panel to remove IIS from your system. To find IIS, click Add/Remove Windows Components.

Impact of Workaround: If you stop the World Wide Web Publishing Service component of IIS, the system can no longer provide Web content. If you stop or remove IIS, the system can no longer provide Web, File Transfer Protocol (FTP), or NTP content. The Simple Mail Transfer Protocol (SMTP) service will also be unavailable.

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FAQ for IIS Redirection Vulnerability - CAN-2004-0205:

What is the scope of the vulnerability?
This is a buffer overrun vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system, including installing programs; viewing, changing, or deleting data; or creating new accounts that have full privileges.

What causes the vulnerability?
The vulnerability is caused by an unchecked buffer in the IIS 4.0 redirect function.

What is a redirect?
By using the IIS 4.0 redirect function, an administrator can forward incoming requests to another virtual directory or to another server.

Does the IIS Lockdown Tool block this attack?
Yes. The IISLockdown tool installs URLScan, which can be used to block this attack. You must configure the URLScan tool by following the steps that are described in the Workarounds for IIS Redirection Vulnerability section of this bulletin to block this attack.

Will the URLScan tool block this attack?
Yes. You can configure the URLScan tool to block this by following the steps that are described in the Workarounds for IIS Redirection Vulnerability section of this bulletin.

What is redirection?
Redirection occurs when a Web browser makes a request for a Web page that does not exist, and the Web server redirects the browser to another page, such as to a generic error page or to the Web site's home page. For example, the Web page http://microsoft.com/xp does not exist, but instead of providing an error, the Web server redirects the browser to a page that suggests pages that the user may have been looking for and provides a site map. This process is redirection.

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

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

How could an attacker exploit the vulnerability?
An attacker could exploit the vulnerability by creating a specially crafted message and sending the message to an affected system, which could then cause the affected system to execute code.

What systems are primarily at risk from the vulnerability?
Systems that have Windows NT 4.0 and IIS 4.0 installed are at risk from this vulnerability. IIS 4.0 is available as part of the Windows NT 4.0 Server Option Pack.

Could the vulnerability be exploited over the Internet?
Yes. An attacker could exploit this vulnerability over the Internet.

What does the update do?
The update removes the vulnerability by modifying the way that IIS 4.0 validates the length of request before it passes the message to the allocated buffer.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft had not received any information indicating 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 indicating 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.

Why is there no update available for Microsoft Windows NT Server 4.0 Terminal Server Edition?
Windows NT 4.0 Option Pack is not supported on Microsoft Windows NT Server 4.0 Terminal Server Edition. For more information see Microsoft Knowledge Base Article 190157.

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Security Update Information

Installation Platforms and Prerequisites:

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

Windows NT 4.0 (all versions)

Prerequisites
This security update requires Windows NT Workstation 4.0 Service Pack 6a (SP6a), or Windows NT Server 4.0 Service Pack 6a (SP6a).

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

For more information about obtaining the latest service pack, see Microsoft Knowledge Base Article 152734.

Installation Information

This security update supports the following setup switches:

/y: Perform removal (only with /m or /q )

/f: Force programs to quit during the shutdown process

/n: Do not create an Uninstall folder

/z: Do not restart when the update completes

/q: Use Quiet or Unattended mode with no user interface (this switch is a superset of /m )

/m: Use Unattended mode with a user interface

/l: List the installed hotfixes

/x: Extract the files without running Setup

Note You can combine these switches into one command. For more information about the supported installation switches, see Microsoft Knowledge Base Article 262841.

Deployment Information

To install the security update without any user intervention, use the following command at a command prompt for Windows NT Server 4.0:

Q841373I.exe

For Windows NT Workstation 4.0:

Q841373I.exe

To install the security update without forcing the system to restart, use the following command at a command prompt for Windows NT Server 4.0:

Q841373I.exe

For Windows NT Workstation 4.0:

Q841373I.exe

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 computer after you apply this security update.

Removal Information

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

System administrators can also use the Hotfix.exe utility to remove this security update. The Hotfix.exe utility is located in the %Windir%\$NTUninstallKB841373$ folder. The Hotfix.exe utility supports the following setup switches:

/y: Perform removal (only with the /m or /q switch)

/f: Force programs to quit during the shutdown process

/n: Do not create an Uninstall folder

/z: Do not restart when the installation is complete

/q: Use Quiet or Unattended mode with no user interface (this switch is a superset of the /m switch)

/m: Use Unattended mode with a user interface

/l: List the installed hotfixes

File Information

The English version of this update has the file attributes (or later) 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.

Note Date, time, file name, or size information could change during installation. See the Verifying Update Installation section for details about how to verify an installation.

Windows NT Workstation 4.0 and Windows NT Server 4.0:

Date Time Version Size File name

05/06/04 12:47p 4.2.788.1 851,456 asp.dll
05/06/04 12:47p 4.2.788.1 140,288 httpodbc.dll
05/06/04 12:47p 4.2.788.1 172,544 iislog.dll
05/06/04 12:47p 4.2.788.1 490,496 infocomm.dll
05/06/04 12:47p 4.2.788.1 67,584 iscomlog.dll
05/06/04 12:47p 4.2.788.1 538,112 w3svc.dll
05/06/04 12:47p 4.2.788.1 219,136 wam.dll
05/06/04 12:47p 4.2.788.1 95,232 ssinc.dll
05/06/04 12:47p 4.2.788.1 61,440 sspifilt.dll
05/06/04 12:47p 4.2.788.1 515,072 adsiis.dll

Windows NT Server 4.0 Terminal Server Edition:

Date Time Version Size File name

05/06/04 12:47p 4.2.788.1 851,456 asp.dll
05/06/04 12:47p 4.2.788.1 140,288 httpodbc.dll
05/06/04 12:47p 4.2.788.1 172,544 iislog.dll
05/06/04 12:47p 4.2.788.1 490,496 infocomm.dll
05/06/04 12:47p 4.2.788.1 67,584 iscomlog.dll
05/06/04 12:47p 4.2.788.1 538,112 w3svc.dll
05/06/04 12:47p 4.2.788.1 219,136 wam.dll
05/06/04 12:47p 4.2.788.1 95,232 ssinc.dll
05/06/04 12:47p 4.2.788.1 61,440 sspifilt.dll
05/06/04 12:47p 4.2.788.1 515,072 adsiis.dll

Verifying Update Installation

• Microsoft Baseline Security Analyzer

To verify that a security update is installed on an affected system, you may be able to use the Microsoft Baseline Security Analyzer (MBSA) tool. This tool 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.

Click Start, and then click Search.

In the Search Results pane, click All files and folders under Search Companion.

In the All or part of the file name box, type a file name from the appropriate file information table, and then click Search.

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.

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 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 the update installation. 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\Windows NT\CurrentVersion\Hotfix\KB841373\File 1

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 841373 security update into the Windows installation source files.

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Obtaining Other Security Updates:

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

• Security updates are available from the Microsoft Download Center: You can find them most easily by doing a keyword search for "security_patch".

• Updates for consumer platforms are available from the Windows Update Web site.

Support:

• Customers in the U.S. and Canada can receive technical support from Microsoft Product Support Services at 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates.

• International customers can receive support from their local Microsoft subsidiaries. There is no charge for support that is associated with security updates. For more information about how to contact Microsoft for support issues, visit the International Support Web site.

Security Resources:

• The Microsoft TechNet Security Web site provides additional information about security in Microsoft products.

• Microsoft Software Update Services

• Microsoft Baseline Security Analyzer (MBSA)

• Windows Update

• Windows Update Catalog: For more information about the Windows Update Catalog, see Microsoft Knowledge Base Article 323166.

• Office Update

Software Update Services:

By using Microsoft Software Update Services (SUS), administrators can quickly and reliably deploy the latest critical updates and security updates to Windows 2000 and Windows Server 2003-based servers, and to desktop systems that are running Windows 2000 Professional or Windows XP Professional.

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

Systems Management Server:

Microsoft Systems Management Server (SMS) delivers a highly-configurable enterprise solution for managing updates. By using SMS, administrators can identify Windows-based systems that require security updates and to perform controlled deployment of these updates throughout the enterprise with minimal disruption to end users. For more information about how administrators can use SMS 2003 to deploy security updates, see the SMS 2003 Security Patch Management Web site. SMS 2.0 users can also use Software Updates Service Feature Pack to help deploy security updates. For information about SMS, visit the SMS Web site.

Note SMS uses the Microsoft Baseline Security Analyzer and the Microsoft Office Detection Tool to provide broad support for security bulletin update detection and deployment. Some software updates may not be detected by these tools. Administrators can use the inventory capabilities of the SMS in these cases to target updates to specific systems. For more information about this procedure, see the following Web site. Some security updates require administrative rights following a restart of the system. Administrators can use the Elevated Rights Deployment Tool (available in the SMS 2003 Administration Feature Pack and in the SMS 2.0 Administration Feature Pack) to install these updates.

Disclaimer:

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions:

• V1.0 (July 13, 2004): Bulletin published