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Microsoft Security Bulletin MS05-034 - Moderate

Cumulative Security Update for ISA Server 2000 (899753)

Published: June 14, 2005

Version: 1.0

Summary

Who should read this document: Customers who use Microsoft Internet Security and Acceleration (ISA) Server 2000

Impact of Vulnerability: Elevation of Privilege

Maximum Severity Rating: Moderate

Recommendation: Customers should consider applying the security update.

Security Update Replacement: None

Caveats: None

Tested Software and Security Update Download Locations:

Affected Software:

  • Microsoft Internet Security and Acceleration (ISA) Server 2000 Service Pack 2 – Download the update

    Note The following software programs include ISA Server 2000. Customers who use these software programs should install the provided ISA Server 2000 security update.

    • Microsoft Small Business Server 2000
    • Microsoft Small Business Server 2003 Premium Edition

Non-Affected Software:

  • Microsoft Internet Security and Acceleration (ISA) Server 2004 Standard Edition
  • Microsoft Internet Security and Acceleration (ISA) Server 2004 Enterprise Edition

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

General Information

Executive Summary:

This update resolves several newly-discovered, privately reported vulnerabilities. Each vulnerability is documented in this bulletin in its own “Vulnerability Details” section of this bulletin.

We recommend that customers consider applying the security update.

Severity Ratings and Vulnerability Identifiers:

Vulnerability IdentifiersImpact of VulnerabilityISA Server 2000
HTTP Content Header Vulnerability - CAN-2005-1215Elevation of Privilege, Cache PoisoningModerate
NetBIOS Predefined Filter Vulnerability - CAN-2005-1216Elevation of PrivilegeModerate
Aggregate Severity of All Vulnerabilities Moderate

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.

Why does this update address several reported security vulnerabilities?
This update contains support for several vulnerabilities because the modifications that are required to address these issues are located in related files. Instead of having to install several updates that are almost the same, customers can install only this update.

Does this update contain any security-related changes to functionality?
Yes. In addition to the changes that are listed in each “Vulnerability Details” sections of this bulletin, this update includes a change in functionality: A Basic Credentials issue as addressed originally in Microsoft Knowledge Base Article 821724 was reintroduced after installing MS04-039, a fix for this issue has been included in this update and the referenced KB article has been updated to reflect this change.

Can I use the Microsoft Baseline Security Analyzer (MBSA) to determine whether this update is required?
No. MBSA does not support ISA Server, and will not detect whether the update is required for that program. However, Microsoft has developed a version of the Enterprise Update Scanning Tool (EST) that will help customers determine if this security update is required.

For detailed information about the programs that MBSA currently does not detect, see Microsoft Knowledge Base Article 306460. For more information about MBSA, visit the MBSA Web site.

What is the Enterprise Update Scanning 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 Scanning Tool (EST) and is designed for enterprise administrators. When a version of the Enterprise Update Scanning 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 Scanning Tool (EST) to determine whether this update is required?
Yes. Microsoft has created a version of the EST that will determine if you have to apply this update. For more information about the version of the EST that is being released this month, see the following Microsoft Web site. For more detailed deployment information about the version of the EST that is being released this month, see the following Microsoft Web site. There is also a version of this tool that SMS customers can obtain by visiting the following Microsoft Web site. This tool may also be available for SMS customers from the SMS 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. SMS uses MBSA for detection; therefore, SMS has the same limitation listed earlier in this bulletin related to programs that MBSA does not detect.

However, there is a version of the EST that SMS customers can obtain that offers an integrated experience for SMS administrators from the following Microsoft Web site.

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

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

You can deploy this update by using the Inventory and Software Distribution feature of SMS.

HTTP Content Header Vulnerability - CAN-2005-1215:

A vulnerability exists in ISA Server 2000 because of the way that it handles malformed HTTP requests. An attacker could exploit the vulnerability by constructing a malicious HTTP request that could potentially allow an attacker to poison the cache of the affected ISA server. As a result, the attacker could either bypass content restrictions and access content that they would normally not have access to or they could cause users to be directed to unexpected content. Additionally, an attacker could use this in combination with a separate Cross Site Scripting vulnerability to obtain sensitive information such as logon credentials.

Mitigating Factors for HTTP Content Header Vulnerability - CAN-2005-1215:

  • An attacker would only be able to poison the cache with existing content from the IP address or domain name of the targeted server
  • Due to the way that caching works, an attacker would need to be able to submit a malicious request before a valid version of the page is cached via another method, either user or automatically invoked.
  • ISA Servers that are configured in Firewall Mode are not vulnerable to this issue.
  • Typical usage of Internet Explorer will not produce malformed HTTP requests.

Workarounds for HTTP Content Header Vulnerability - CAN-2005-1215:

We have not identified any workarounds for this vulnerability.

FAQ for HTTP Content Header Vulnerability - CAN-2005-1215:

What is the scope of the vulnerability?
This is an elevation of privilege vulnerability. An attacker who successfully exploited this vulnerability could either bypass content restrictions and access content that they would normally not have access to or they could cause users to be directed to unexpected content. Additionally, an attacker could use this in conjunction with a separate Cross Site Scripting vulnerability to obtain sensitive information such as logon credentials.

What causes the vulnerability?
The process used by ISA Server to handle multiple HTTP content length headers.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could poison the ISA cache or bypass content restriction policies.

Who could exploit the vulnerability?
In order to attempt to exploit this vulnerability, an attacker must be able to send a malformed http request packet to an ISA Server which has been either configured to publish a web server or proxy web content. The source of the attack would determine the scope of the affected clients. In a web publishing scenario, clients attempting to view the contents of the published Web Site could be directed to unexpected content. In a web caching configuration, clients could be directed to unexpected content from external web content previously cached.

What is ISA Server 2000?
ISA Server 2000 provides an enterprise firewall and a high-performance Web cache. The firewall helps protect the network by regulating which resources can be accessed through the firewall, and under what conditions. The Web cache helps improve network performance by storing local copies of frequently-requested Web content. ISA Server can be installed in three modes: firewall mode, cache mode, and integrated mode.Firewall mode allows an administrator to secure network communication by configuring rules that control communication between the corporate network and the Internet. Cache mode improves network performance by storing frequently-accessed Web pages on the server. In integrated mode, all cache and firewall features are available.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by creating a specially crafted HTTP request packet and sending the packet to an affected ISA Server.

What systems are primarily at risk from the vulnerability?
ISA Servers that are configured to cache Web requests or to publish Web servers.

What does the update do?
The update removes the vulnerability by modifying the way that ISA Server handles HTTP request packets that have multiple content-length headers.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
Yes. This vulnerability has been publicly disclosed. However, it had not been assigned Common Vulnerability and Exposure number. This type of vulnerability has also been named “HTTP Smuggling” by the larger security community.

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

NetBIOS Predefined Filter Vulnerability - CAN-2005-1216:

An elevation of privilege vulnerability exists in ISA Server 2000 that could allow an attacker who successfully exploited this vulnerability to create a NetBIOS connection with an ISA Server by utilizing the NetBIOS (all) predefined packet filter. The attacker would be limited to services that use the NetBIOS protocol running on the affected ISA Server.

Mitigating Factors for NetBIOS Predefined Filter Vulnerability - CAN-2005-1216:

An ISA administrator would have to enable the NetBIOS (all) predefined packet filter to allow access to local services that use the NetBIOS protocol.

Workarounds for NetBIOS Predefined Filter Vulnerability - CAN-2005-1216:

We have not identified any workarounds for this vulnerability.

FAQ for NetBIOS Predefined Filter Vulnerability - CAN-2005-1216:

What is the scope of the vulnerability?
This is an elevation of privilege vulnerability. An attacker who successfully exploited this vulnerability could connect to services utilizing the NetBIOS protocol on the affected ISA Server.

What causes the vulnerability?
The process used by ISA Server to validate NetBIOS connections through the NetBIOS (all) predefined packet filter.

What is NetBIOS?
NetBIOS is a set of networking services for computer networking. NetBIOS can be implemented on top of a number of different networking protocols, such as TCP/IP.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could connect to services on the ISA Server that use the NetBIOS protocol. However, these connection attempts are subject to the typical security checks that are employed by the respective services.

Who could exploit the vulnerability?
On ISA Server 2000, any anonymous user who could create a NetBIOS connection to the affected ISA Server could try to exploit this vulnerability.

What is ISA Server 2000?
ISA Server 2000 provides an enterprise firewall and a high-performance Web cache. The firewall helps protect the network by regulating which resources can be accessed through the firewall, and under what conditions. The Web cache helps improve network performance by storing local copies of frequently-requested Web content.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by creating a NetBIOS connection with an ISA Server that uses the NetBIOS (all) predefined packet filter. The attacker would be limited to services by using the NetBIOS protocol running on the affected ISA Server.

What systems are primarily at risk from the vulnerability?
ISA Servers that have been configured to allow inbound NetBIOS traffic by using the NetBIOS (all) predefined packet filter are primarily at risk from this vulnerability.

What does the update do?
The update addresses the vulnerability by modifying the process that ISA Server uses to validate NetBIOS connections through the NetBIOS (all) predefined packet filter.

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:

ISA Server 2000 Service Pack 2, Small Business Server 2000, Small Business Server 2000 Service Pack 1, Small Business Server 2003

Prerequisites
This security update requires ISA Server 2000 Service Pack 2 (SP2)

Inclusion in Future Service Packs:
The update for this issue may be included in a future service pack.

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, use the following command at a command prompt for ISA Server 2000:

ISA2000-KB899753-X86-ENU.exe

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 in use, this update will require a restart. If this occurs, a message appears that advises you to restart.

Removal Information

To remove this update, use the Add or Remove Programs tool in Control Panel. Select Security Update for Microsoft ISA Server 2000 (899753), and then click Add/Remove.

System administrators can also use the Spuninst.exe utility to remove this security update. The Spuninst.exe utility is located in the %Windir%\$NTUninstallKB899753$\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.

ISA Server 2000 Service Pack 2, Small Business Server 2000, Small Business Server 2000 Service Pack 1, Small Business Server 2003:

File NameVersionDateTimeSize
Mspadmin.exe3.0.1200.43023-May-200520:23185,336
W3proxy.exe3.0.1200.43023-May-200520:23402,424
Wspsrv.exe3.0.1200.43023-May-200520:23307,192

Verifying Update Installation

  • 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 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 keys.

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fpc\Hotfixes\SP1\430

  • Alternatively you can follow these steps to verify that the security update has installed:
    1. Click Start, click Settings, and then click Control Panel.
    2. Double-click Add/Remove Programs.
    3. If Security Update for Microsoft ISA Server 2000 (KB899753) appears in the list, the security update has been successfully installed.

Other Information

Acknowledgments

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

  • Steve Orrin of Watchfire for reporting the HTTP Content Header Vulnerability (CAN-2005-1215).
  • Han Valk for reporting the Basic Credentials issue.

Obtaining Other Security Updates:

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

Support:

  • Customers in the U.S. and Canada can receive technical support from Microsoft Product Support Services at 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates.
  • International customers can receive support from their local Microsoft subsidiaries. There is no charge for support that is associated with security updates. For more information about how to contact Microsoft for support issues, visit the International Support Web site.

Security Resources:

Software Update Services:

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

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

Systems Management Server:

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

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

Disclaimer:

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

Revisions:

  • V1.0 (June 14, 2005): Bulletin published

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