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Microsoft Security Bulletin MS06-033 - Important

Vulnerability in ASP.NET Could Allow Information Disclosure (917283)

Published: July 11, 2006 | Updated: November 29, 2006

Version: 1.3

Summary

Who Should Read this Document: Customers who use Microsoft Windows NET Framework 2.0

Impact of Vulnerability: Information Disclosure

Maximum Severity Rating: Important

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

Security Update Replacement: None

Caveats: Microsoft Knowledge Base Article 917283 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 917283.

Tested Software and Security Update Download Locations:

Affected Software:

.NET Framework 2.0 for the following operating system versions: –Download the update (KB922481)

  • Microsoft Windows 2000 Service Pack 4
  • Microsoft Windows XP Service Pack 1 or Windows XP Service Pack 2
  • Microsoft Windows XP Professional x64 Edition
  • Microsoft Windows XP Tablet PC Edition
  • Microsoft Windows XP Media Center Edition
  • Microsoft Windows Server 2003 or Windows Server 2003 Service Pack 1
  • Microsoft Windows Server 2003 for Itanium-based systems and Microsoft Windows Server with SP1 for Itanium-based Systems
  • Microsoft Windows Server 2003 x64 Edition

Non-Affected Software:

  • Microsoft .NET Framework 1.0
  • Microsoft .NET Framework 1.1
  • Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and Microsoft Windows Millennium Edition (Me)

Tested Microsoft Windows Components:

Affected Components:

  • ASP.NET

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.

Note The security updates for Microsoft Windows Server 2003, Windows Server 2003 Service Pack 1, and Windows Server 2003 x64 Edition also apply to Windows Server 2003 R2.

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.

This vulnerability could allow an attacker to bypass ASP.Net security and gain unauthorized access to objects in the Application folder explicitly by name. 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.

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

Severity Ratings and Vulnerability Identifiers:

Vulnerability IdentifiersImpact of Vulnerability.NET Framework 2.0
.NET 2.0 Application Folder Information Disclosure Vulnerability - CVE-2006-1300Information DisclosureImportant

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.

Note The security updates for Microsoft Windows Server 2003, Windows Server 2003 Service Pack 1, and Windows Server 2003 x64 Edition also apply to Windows Server 2003 R2.

Note The severity ratings for non-x86 operating system versions map to the x86 operating systems versions as follows:

  • The Microsoft Windows XP Professional x64 Edition severity rating is the same as the Windows XP Service Pack 2 severity rating.
  • The Microsoft Windows Server 2003 for Itanium-based Systems severity rating is the same as the Windows Server 2003 severity rating.
  • The Microsoft Windows Server 2003 with SP1 for Itanium-based Systems severity rating is the same as the Windows Server 2003 Service Pack 1 severity rating.
  • The Microsoft Windows Server 2003 x64 Edition severity rating is the same as the Windows Server 2003 Service Pack 1 severity rating.

What are the known issues that customers may experience when they install this security update?

Microsoft Knowledge Base Article 917283 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 917283.

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 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.

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

ProductMBSA 1.2.1Enterprise Update Scan Tool (EST)MBSA 2.0
.NET Framework 2.0 NoYesYes

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

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 the EST that will determine if you have to apply this update. For download links and more information about the version of the EST that is being released this month, see the following Microsoft Web site. SMS customers should review the "Can I use Systems Management Server (SMS) to determine whether this update is required?" FAQ 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 summary for this security update.

ProductSMS 2.0SMS 2003
.NET Framework 2.0 Yes (with the EST)Yes

SMS uses MBSA for detection. Therefore, SMS has the same limitation that is listed earlier in this bulletin related to software that MBSA does not detect.

For SMS 2.0, the SMS SUS Feature Pack, which includes the Security Update Inventory Tool, can be used by SMS to detect security updates. SMS SUIT uses the MBSA 1.2.1 engine for detection. For more information about the Security Update Inventory Tool, visit the following Microsoft Web site. For more information about the limitations of the Security Update Inventory Tool, 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 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 Inventory Tool for Microsoft Updates, 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.

.NET 2.0 Application Folder Information Disclosure Vulnerability - CVE-2006-1300

This Information Disclosure vulnerability could allow an attacker to bypass ASP.Net security and gain unauthorized access to objects in the Application folders explicitly by name. 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.

Mitigating Factors for .NET 2.0 Application Folder Vulnerability - CVE-2006-1300:

  • Directory browsing is not enabled by default on Application folder directories. An attacker would have to guess or know the names of the files they are attempting to retrieve or view.
  • By default, file extensions that are used by Visual Studio and ASP.NET web projects are mapped to the aspnet_isapi.dll System.Web.HttpForbiddenHandler and as a result, files with these extensions cannot be retrieved or viewed remotely using this vulnerability.

    Here's the full list of file extensions that are protected (and not vulnerable): *.asax, *.ascx, *.master, *.skin, *.browser, *.sitemap, *.config (but not *.exe.config or *.dll.config), *.cs, *.csproj, *.vb, *.vbproj, *.webinfo, *.licx, *.resx, *.resources, *.mdb, *.vjsproj, *.java, *.dd, *.jsl, *.ldb, *.ad, *.ldd, *.sd, *.cd, *.adprototype, *.lddprototype, *.sdm, *.sdmDocument, *.mdf, *.ldf, *.exclude, *.refresh

  • IIS 6.0 will not send any file types that do not have a MIME mapping defined for the IIS 6.0. IIS 6.0 only stores the allowed MIME mappings in the metabase.

    For example if a custom file type with a .data file extension is located in the ‘app_data’ folder on an IIS6 server, but there is no MIME association for .data files defined in IIS or the Windows Registry on that server, Internet Information Services (IIS) will not serve this type of file and will return a 404 error (regardless of what folder / directory the file resides in).

  • Customers using URLScan who have followed the guidance in Knowledge Base Article 815155 for hardening ASP.NET web applications are at less risk from this vulnerability.

Workarounds for .NET 2.0 Application Folder Vulnerability - CVE-2006-1300

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

  • Remove “Read” permission from all ASP.NET 2.0 Application folders.
    Removal of the “Read” permissions for Web content helps protect the affected system from attempts to exploit this vulnerability.

To set permissions for Web content on Windows 2000 running IIS5.0 using the Microsoft Management Console (MMC):

  1. Click Start, then click Run and then type: %systemroot%\system32\inetsrv\iis.msc
  2. When the ‘Internet Information Services’ MMC snap-in loads, in the left pane, click the plus (+) sign next to the computer name to expand the list of web sites hosted on that server.
  3. Expand the first web site by clicking the plus (+) sign next to it.
  4. For each ASP.NET 2.0 ‘Application Folder’, right click on the folder and select ‘Properties’
    For a complete list of ASP.NET 2.0 ‘Application Folders’ visit this website.
  5. On the ‘Directory’ or ‘Virtual Directory’ tab clear the checkbox next to ‘Read’ and press ‘OK
  6. Repeat step 3 for each web site and application hosted on the server.

To set permissions for Web content on Windows 2003 with IIS 6.0 using the Microsoft Management Console (MMC):

  1. Click Start, click Run and then type: %systemroot%\system32\inetsrv\iis.msc
  2. When the ‘Internet Information Services’ MMC snap-in is finished loading, in the left pane, click the plus (+) sign next to the computer name
  3. Click the plus (+) sign next to the ‘Web sites’ folder to expand the list of web sites hosted on that server.
  4. Expand the first web site by clicking the plus (+) sign next to it.
  5. For each ASP.NET 2.0 ‘Application Folder’, right click on the folder and select ‘Properties’
    For a complete list of ASP.NET 2.0 ‘Application Folders’ visit this website.
  6. On the ‘Directory’ or ‘Virtual Directory’ tab clear the checkbox next to ‘Read’ and press ‘OK
  7. Repeat step 4 for each web site and application hosted on the server.

Impact of Workaround: Denying read access on the virtual directory would block reflection and therefore inhibits remote debugging.

  • Use URLScan with the DenyUrlSequences setting to disallow URLs that request protected file extensions.
    1. If URLScan is already installed, make a backup copy of the URLScan.ini before continuing to the next step.
    2. Configure the URLScan.ini (located in the %windir%\system32\inetsrv\urlscan folder by default) with the following settings:
    3. In the [Options] section, ensure that NormalizeUrlBeforeScan is set to 1
    4. In the [Options] section, ensure that VerifyNormalization is set to 1
    5. In the [DenyUrlSequences] section, ensure that the backslash ‘\’ character is listed
    6. Re-start IIS for the changes to take effect.

Note The above settings are enabled by default in versions of URLScan installed by the IIS Lockdown wizard and for all stand-alone installations of URLScan 2.5.

Note For additional information on configuring URLScan to work with ASP.NET applications refer to Knowledge Base Article 815155.

Impact of Workaround: Improper configuration of URLScan could prevent some web applications from functioning properly.

  • Use file extensions for files in the App_* folders that are not mapped to ASP.NET and that have no MIME type mapping that IIS can use.
    If a static file extension has no MIME type mapping Internet Information Services 6.0 (IIS) will not serve it.

Impact of Workaround: None

FAQ for .NET 2.0 Application Folder Vulnerability - CVE-2006-1300:

What is the scope of the vulnerability?
This information disclosure vulnerability could allow an attacker to bypass ASP.Net security and gain unauthorized access to objects in the Application folder explicitly by name. 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?
ASP .NET 2.0 does not properly validate the URL passed.

What is ASP.NET
ASP.NET is collection of technologies within the.NET Framework that enable developers to build Web applications and XML Web Services.
Unlike traditional Web pages, which use a combination of static HTML and scripting, ASP.NET uses compiled, event-driven pages. This enables developers to build Web-based applications with the same richness and functionality usually associated with applications built in languages such as Visual Basic or Visual C++. Because ASP.NET is a Web-based application environment, it requires an underlying Web server to provide basic HTTP functionality. For this reason, ASP.NET runs on top of IIS 5.0 on Windows 2000, IIS 5.1 on Windows XP and IIS 6.0 on Windows Server 2003.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain unauthorized access to parts of a Web site. The actions the attacker could take would depend on the specific content being protected.

Who could exploit the vulnerability?
In a Web-based attack scenario, an attacker would have to have access to a Web site that contains an Application Folder to attempt to exploit this vulnerability. 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 systems are primarily at risk from the vulnerability?
Internet facing systems are primarily at risk from this vulnerability. In addition, internal Web sites that use ASP.NET to host sensitive data can be 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.

What does the update do?
The update removes the vulnerability by modifying the way that ASP.NET validates URL paths.

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:

The Microsoft .NET Framework version 2.0

Prerequisites
This security update requires the Microsoft .NET Framework version 2.0

Microsoft Windows Installer 3.1 must be installed. To install the latest version of Windows Installer, visit the following Microsoft Web site:

Windows Installer 3.1 Redistributable (v2)

Inclusion in Future Service Packs:
The update for this issue is included in The Microsoft .NET Framework version 2.0 Service Pack 1.

Installation Information

This security update supports the following setup switches.

Supported Security Update Installation Switches
SwitchDescription
/help Displays the command-line options.
Setup Modes
/quiet Quiet mode. This is the same as unattended mode, but no status or error messages are displayed.
Restart Options
/norestart Does not restart when installation has completed.
/forcerestart Restarts the computer after installation and forces other applications to close at shutdown without saving open files first.
/warnrestart[:x] Displays a dialog box with a timer warning the user that the computer will restart in x seconds. (The default setting is 30 seconds.) Intended for use with the /quiet switch or the /passive switches.
/promptrestart Display a dialog box prompting the local user to allow a restart.
Special Options
/overwriteoem Overwrites OEM files without prompting.
/nobackup Does not back up files needed for uninstallation.
/forceappsclose Forces other programs to close when the computer shuts down.
/log:path Allows the redirection of installation log files.
/integrate:path Integrates the update into the Windows source files. These files are located at the path that is specified in the switch.
/extract[:path] Extracts files without starting the Setup program.
/ER Enables extended error reporting.
/verbose Enables verbose logging. During installation, creates %Windir%\CabBuild.log. This log details the files that are copied. Using this switch may cause the installation to proceed more slowly.

Note You can combine these switches into one command. For backward compatibility, the security update also supports the setup switches that the earlier version of the Setup program uses. For more information about the supported installation switches, see Microsoft Knowledge Base Article 262841. For more information about the Update.exe installer, visit the Microsoft TechNet Web site.

Deployment Information

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

NDP20-KB917283-x86.exe /quiet

NDP20-KB917283-x64.exe /quiet

NDP20-KB917283-xia64.exe /quiet

Note Use of the /quiet switch will suppress all messages. This includes suppressing failure messages. Administrators should use one of the supported methods to verify the installation was successful when they use the /quiet switch. Administrators should also review the KB917283.log file for any failure messages when they use this switch.

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

NDP20-KB917283-x86.exe /norestart

NDP20-KB917283-x64.exe /norestart

NDP20-KB917283-xia64.exe /quiet

For more information about how to deploy this security update with 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 be required, stop all affected services and close all applications that may use the affected files prior to installing the security update. For more information about the reasons why you may be prompted to restart your computer, see Microsoft Knowledge Base Article 887012.

Removal Information
To remove this update, use the Add or Remove Programs tool in Control Panel.

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.

The Microsoft .NET Framework version 2.0

File NameVersionDateTimeSize
Aspnet_filter.dll2.0.50727.10114-Apr-200606:0810,752

The Microsoft .NET Framework version 2.0 on Windows Server, 2003 Enterprise Edition for Itanium-based Systems; Windows Server 2003, Datacenter Edition for Itanium-based Systems; Windows Server 2003, Enterprise Edition with SP1 for Itanium-based Systems; and Windows Server 2003, Datacenter Edition with SP1 for Itanium-based Systems:

File NameVersionDateTimeSize
Aspnet_filter.dll2.0.50727.10114-Apr-200604:0334,304

The Microsoft .NET Framework version 2.0 for Windows Server 2003, Standard x64 Edition; Windows Server 2003, Enterprise x64 Edition; and Windows Server 2003, Datacenter x64 Edition; Windows Server 2003 R2, Standard x64 Edition; Windows Server 2003 R2, Enterprise x64 Edition; and Windows Server 2003 R2, Datacenter x64 Edition:

File NameVersionDateTimeSize
Aspnet_filter.dll2.0.50727.10114-Apr-200606:0810,752

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.
    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.

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

Windows Server Update Services:

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

For more information about how to deploy security updates using Windows Server Update Services, visit the Windows Server Update Services Web site.

Systems Management Server:

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

Note SMS uses the Microsoft Baseline Security Analyzer, the Microsoft Office Detection Tool, and the Enterprise Update 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 (July 11, 2006): Bulletin published.
  • V1.1 (July 11, 2006): Bulletin updated “Caveats” Section.
  • V1.2 (July 19, 2006): Bulletin updated “Caveats” Section. Provided additional clarity around “Prerequisites” and “Installation Information” for “The Microsoft .NET Framework version 2.0” under the “Security Update Information” Section.
  • V1.3 (November 29, 2006): Bulletin updated “Caveats” Section and “What are the known issues that customers may experience when they install this security update?” under the “Frequently Asked Questions (FAQ) Related to This Security Update” section.

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