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Microsoft Security Bulletin MS12-069 - Important

Vulnerability in Kerberos Could Allow Denial of Service (2743555)

Published: October 09, 2012 | Updated: May 29, 2013

Version: 1.1

General Information

Executive Summary

This security update resolves a privately reported vulnerability in Microsoft Windows. The vulnerability could allow denial of service if a remote attacker sends a specially crafted session request to the Kerberos server. 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.

This security update is rated Important for all supported editions of Windows 7 and Windows Server 2008 R2. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerability by correcting how the Microsoft Kerberos implementation handles a specially crafted session. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section, Vulnerability Information.

Recommendation. Most customers have automatic updating enabled and will not need to take any action because this security update will be downloaded and installed automatically. Customers who have not enabled automatic updating need to check for updates and install this update manually. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.

For administrators and enterprise installations, or end users who want to install this security update manually, Microsoft recommends that customers apply the update at the earliest opportunity using update management software, or by checking for updates using the Microsoft Update service.

See also the section, Detection and Deployment Tools and Guidance, later in this bulletin.

Known Issues. None

Affected and Non-Affected Software

The following software have been tested to determine which versions or editions are affected. Other versions or editions are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.

Affected Software 

Operating SystemMaximum Security ImpactAggregate Severity RatingUpdates Replaced
Windows 7
Windows 7 for 32-bit Systems
(KB2743555)
Denial of ServiceImportantKB2425227 in MS11-013 replaced by KB2743555
Windows 7 for 32-bit Systems Service Pack 1
(KB2743555)
Denial of ServiceImportantKB2425227 in MS11-013 replaced by KB2743555
Windows 7 for x64-based Systems
(KB2743555)
Denial of ServiceImportantKB2425227 in MS11-013 replaced by KB2743555
Windows 7 for x64-based Systems Service Pack 1
(KB2743555)
Denial of ServiceImportantKB2425227 in MS11-013 replaced by KB2743555
Windows Server 2008 R2
Windows Server 2008 R2 for x64-based Systems
(KB2743555)
Denial of ServiceImportantNone
Windows Server 2008 R2 for x64-based Systems Service Pack 1
(KB2743555)
Denial of ServiceImportantNone
Windows Server 2008 R2 for Itanium-based Systems
(KB2743555)
Denial of ServiceImportantKB2425227 in MS11-013 replaced by KB2743555
Windows Server 2008 R2 for Itanium-based Systems Service Pack 1
(KB2743555)
Denial of ServiceImportantKB2425227 in MS11-013 replaced by KB2743555
Server Core installation option
Windows Server 2008 R2 for x64-based Systems (Server Core installation)
(KB2743555)
Denial of ServiceImportantNone
Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)
(KB2743555)
Denial of ServiceImportantNone

 

Non-Affected Software

Operating System
Windows XP Service Pack 3
Windows XP Professional x64 Edition Service Pack 2
Windows Server 2003 Service Pack 2
Windows Server 2003 x64 Edition Service Pack 2
Windows Server 2003 with SP2 for Itanium-based Systems
Windows Vista Service Pack 2
Windows Vista x64 Edition Service Pack 2
Windows Server 2008 for 32-bit Systems Service Pack 2
Windows Server 2008 for x64-based Systems Service Pack 2
Windows Server 2008 for Itanium-based Systems Service Pack 2
Windows 8 for 32-bit Systems
Windows 8 for 64-bit Systems
Windows Server 2012
Server Core installation option
Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)
Windows Server 2012 (Server Core installation)

Where are the file information details? 
Refer to the reference tables in the Security Update Deployment section for the location of the file information details.

Where are the hashes of the security update? 
The SHA1 and SHA2 hashes of the security update can be used to verify the authenticity of downloaded security update packages. For the hash information pertaining to this update, see Microsoft Knowledge Base Article KB2743555.

I am using an older release of the software discussed in this security bulletin. What should I do? 
The affected software listed in this bulletin have been tested to determine which releases are affected. Other releases are past their support life cycle. For more information about the product lifecycle, see the Microsoft Support Lifecycle website.

It should be a priority for customers who have older releases of the software to migrate to supported releases to prevent potential exposure to vulnerabilities. To determine the support lifecycle for your software release, see Select a Product for Lifecycle Information. For more information about service packs for these software releases, see Service Pack Lifecycle Support Policy.

Customers who require custom support for older software 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, see the Microsoft Worldwide Information website, select the country in the Contact Information list, 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 Microsoft Support Lifecycle Policy FAQ.

Vulnerability Information

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the October bulletin summary. For more information, see Microsoft Exploitability Index.

Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected SoftwareKerberos NULL Dereference Vulnerability - CVE-2012-2551Aggregate Severity Rating
Windows 7
Windows 7 for 32-bit SystemsImportant 
Denial of Service
Important
Windows 7 for 32-bit Systems Service Pack 1Important 
Denial of Service
Important
Windows 7 for x64-based SystemsImportant 
Denial of Service
Important
Windows 7 for x64-based Systems Service Pack 1Important 
Denial of Service
Important
Windows Server 2008 R2
Windows Server 2008 R2 for x64-based SystemsImportant 
Denial of Service
Important
Windows Server 2008 R2 for x64-based Systems Service Pack 1Important 
Denial of Service
Important
Windows Server 2008 R2 for Itanium-based SystemsImportant 
Denial of Service
Important
Windows Server 2008 R2 for Itanium-based Systems Service Pack 1Important 
Denial of Service
Important
Server Core installation option
Windows Server 2008 R2 for x64-based Systems (Server Core installation)Important 
Denial of Service
Important
Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)Important 
Denial of Service
Important

A denial of service vulnerability exists when the Microsoft Kerberos implementation fails to properly handle a specially crafted session. An attacker who successfully exploited this vulnerability could cause the system to stop responding and restart.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2012-2551.

Mitigating Factors for Kerberos NULL Dereference Vulnerability - CVE-2012-2551

Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability. The following mitigating factors may be helpful in your situation:

  • 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.

Workarounds for Kerberos NULL Dereference Vulnerability - CVE-2012-2551

Microsoft has not identified any workarounds for this vulnerability.

FAQ for Kerberos NULL Dereference Vulnerability - CVE-2012-2551

What is the scope of the vulnerability? 
This is a denial of service vulnerability. An attacker who exploited this vulnerability could cause the affected system to restart. Note that this vulnerability would not allow an attacker to execute code or to elevate user rights.

What causes the vulnerability? 
The vulnerability is caused when the Microsoft Kerberos implementation in Microsoft Windows fails to properly handle a specially crafted session.

What is Kerberos? 
Kerberos is a protocol used to mutually authenticate users and services on an open and unsecured network. It allows services to correctly identify the user of a Kerberos ticket without having to authenticate the user at the service. It does this by using shared secret keys.

The Kerberos protocol uses shared secret keys to encrypt and sign users' credentials. A client is authenticated by a Kerberos Key Distribution Center (KDC). After that authentication, the user can request a service ticket to access a specific service on the network. This ticket includes the encrypted authenticated identity of the user.

What might an attacker use the vulnerability to do? 
An attacker who successfully exploited this vulnerability could cause the affected system to restart.

How could an attacker exploit the vulnerability? 
A remote attacker could exploit this vulnerability by sending a specially crafted session request to the Kerberos server.

What systems are primarily at risk from the vulnerability? 
Workstations and servers are primarily at risk from this vulnerability.

What does the update do? 
The update addresses the vulnerability by correcting how the Microsoft Kerberos implementation handles a specially crafted session.

When this security bulletin was issued, had this vulnerability been publicly disclosed? 
No. Microsoft received information about this vulnerability through coordinated vulnerability disclosure.

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 when this security bulletin was originally issued.

Update Information

Security Central

Manage the software and security updates you need to deploy to the servers, desktop, and mobile systems in your organization. For more information see the TechNet Update Management Center. The Microsoft TechNet Security website provides additional information about security in Microsoft products.

Security updates are available from Microsoft Update and Windows Update. Security updates are also available from the Microsoft Download Center. You can find them most easily by doing a keyword search for "security update."

Finally, security updates can be downloaded from the Microsoft Update Catalog. The Microsoft Update Catalog provides a searchable catalog of content made available through Windows Update and Microsoft Update, including security updates, drivers and service packs. By searching using the security bulletin number (such as, "MS12-001"), you can add all the applicable updates to your basket (including different languages for an update), and download to the folder of your choosing. For more information about the Microsoft Update Catalog, see the Microsoft Update Catalog FAQ.

Detection and Deployment Guidance

Microsoft provides detection and deployment guidance for security updates. This guidance contains recommendations and information that can help IT professionals understand how to use various tools for detection and deployment of security updates. For more information, see Microsoft Knowledge Base Article 961747.

Microsoft Baseline Security Analyzer

Microsoft Baseline Security Analyzer (MBSA) lets administrators scan local and remote systems for missing security updates as well as common security misconfigurations. For more information, see Microsoft Baseline Security Analyzer.

The following table provides the MBSA detection summary for this security update.

Software MBSA
Windows 7 for 32-bit Systems and Windows 7 for 32-bit Systems Service Pack 1Yes
Windows 7 for x64-based Systems and Windows 7 for x64-based Systems Service Pack 1Yes
Windows Server 2008 R2 for x64-based Systems and Windows Server 2008 R2 for x64-based Systems Service Pack 1Yes
Windows Server 2008 R2 for Itanium-based Systems and Windows Server 2008 R2 for Itanium-based Systems Service Pack 1Yes

Note For customers using legacy software not supported by the latest release of MBSA, Microsoft Update, and Windows Server Update Services, please see Microsoft Baseline Security Analyzer and reference the Legacy Product Support section on how to create comprehensive security update detection with legacy tools.

Windows Server Update Services

Windows Server Update Services (WSUS) enables information technology administrators to deploy the latest Microsoft product updates to computers that are running the Windows operating system. For more information about how to deploy security updates using Windows Server Update Services, see the TechNet article, Windows Server Update Services.

Systems Management Server

The following table provides the SMS detection and deployment summary for this security update.

SoftwareSMS 2003 with ITMUSystem Center Configuration Manager
Windows 7 for 32-bit Systems and Windows 7 for 32-bit Systems Service Pack 1YesYes
Windows 7 for x64-based Systems and Windows 7 for x64-based Systems Service Pack 1YesYes
Windows Server 2008 R2 for x64-based Systems and Windows Server 2008 R2 for x64-based Systems Service Pack 1YesYes
Windows Server 2008 R2 for Itanium-based Systems and Windows Server 2008 R2 for Itanium-based Systems Service Pack 1YesYes

Note Microsoft discontinued support for SMS 2.0 on April 12, 2011. For SMS 2003, Microsoft also discontinued support for the Security Update Inventory Tool (SUIT) on April 12, 2011. Customers are encouraged to upgrade to System Center Configuration Manager. For customers remaining on SMS 2003 Service Pack 3, the Inventory Tool for Microsoft Updates (ITMU) is also an option.

For SMS 2003, the SMS 2003 Inventory Tool for Microsoft Updates (ITMU) can be used by SMS to detect security updates that are offered by Microsoft Update and that are supported by Windows Server Update Services. For more information about the SMS 2003 ITMU, see SMS 2003 Inventory Tool for Microsoft Updates. For more information about SMS scanning tools, see SMS 2003 Software Update Scanning Tools. See also Downloads for Systems Management Server 2003.

System Center Configuration Manager uses WSUS 3.0 for detection of updates. For more information, see System Center.

For more detailed information, see Microsoft Knowledge Base Article 910723: Summary list of monthly detection and deployment guidance articles.

Update Compatibility Evaluator and Application Compatibility Toolkit

Updates often write to the same files and registry settings required for your applications to run. This can trigger incompatibilities and increase the time it takes to deploy security updates. You can streamline testing and validating Windows updates against installed applications with the Update Compatibility Evaluator components included with Application Compatibility Toolkit.

The Application Compatibility Toolkit (ACT) contains the necessary tools and documentation to evaluate and mitigate application compatibility issues before deploying Windows Vista, a Windows Update, a Microsoft Security Update, or a new version of Windows Internet Explorer in your environment.

Affected Software

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

Windows 7 (all editions)

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.

Inclusion in Future Service PacksThe update for this issue will be included in a future service pack or update rollup
Deployment 
Installing without user interventionFor all supported 32-bit editions of Windows 7:
Windows6.1-KB2743555-x86.msu /quiet
For all supported x64-based editions of Windows 7:
Windows6.1-KB2743555-x64.msu /quiet
Installing without restartingFor all supported 32-bit editions of Windows 7:
Windows6.1-KB2743555-x86.msu /quiet /norestart
For all supported x64-based editions of Windows 7:
Windows6.1-KB2743555-x64.msu /quiet /norestart
Further informationSee the subsection, Detection and Deployment Tools and Guidance
Restart Requirement 
Restart required?Yes, you must restart your system after you apply this security update.
HotPatchingNot applicable.
Removal InformationTo uninstall an update installed by WUSA, use the /Uninstall setup switch or click Control Panel, click System and Security, and then under Windows Update, click View installed updates and select from the list of updates.
File InformationSee Microsoft Knowledge Base Article 2743555
Registry Key VerificationNote A registry key does not exist to validate the presence of this update.

Deployment Information

Installing the Update

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

For more information about the terminology that appears in this bulletin, such as hotfix, see Microsoft Knowledge Base Article 824684.

This security update supports the following setup switches.

Supported Security Update Installation Switches
SwitchDescription
/?, /h, /helpDisplays help on supported switches.
/quietSuppresses the display of status or error messages.
/norestartWhen combined with /quiet, the system will not be restarted after installation even if a restart is required to complete installation.
/warnrestart:<seconds>When combined with /quiet, the installer will warn the user before initiating restart.
/promptrestartWhen combined with /quiet, the installer will prompt before initiating restart.
/forcerestartWhen combined with /quiet, the installer will forcefully close applications and initiate restart.
/log:<file name>Enables logging to specified file.
/extract:<destination>Extracts the package contents to the destination folder.
/uninstall /kb:<KB Number>Uninstalls the security update.

Note For more information about the wusa.exe installer, see "Windows Update Stand-alone Installer" in the TechNet article, Miscellaneous Changes in Windows 7.

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. See the section, Detection and Deployment Tools and Guidance, earlier in this bulletin for more information.

  • File Version Verification

    Because there are several editions of Microsoft Windows, the following steps may be different on your system. If they are, see your product documentation to complete these steps.

    1. Click Start and then enter an update file name in the Search box.
    2. When the file appears under Programs, right-click the file name and click Properties.
    3. On the General tab, compare the file size with the file information tables provided in the bulletin KB article.

      Note Depending on the edition of the operating system, or the programs that are installed on your system, some files that are listed in the file information table may not be installed.
    4. You can also click the Details tab and compare information, such as file version and date modified, with the file information tables provided in the bulletin KB article.

      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.
    5. Finally, you can also click the Previous Versions tab and compare file information for the previous version of the file with the file information for the new, or updated, version of the file.

Windows Server 2008 R2 (all editions)

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.

Inclusion in Future Service PacksThe update for this issue will be included in a future service pack or update rollup
Deployment 
Installing without user interventionFor all supported x64-based editions of Windows Server 2008 R2:
Windows6.1-KB2743555-x64.msu /quiet
For all supported Itanium-based editions of Windows Server 2008 R2:
Windows6.1-KB2743555-ia64.msu /quiet
Installing without restartingFor all supported x64-based editions of Windows Server 2008 R2:
Windows6.1-KB2743555-x64.msu /quiet /norestart
For all supported Itanium-based editions of Windows Server 2008 R2:
Windows6.1-KB2743555-ia64.msu /quiet /norestart
Further informationSee the subsection, Detection and Deployment Tools and Guidance
Restart Requirement 
Restart required?Yes, you must restart your system after you apply this security update.
HotPatchingNot applicable.
Removal InformationTo uninstall an update installed by WUSA, use the /Uninstall setup switch or click Control Panel, click System and Security, and then under Windows Update, click View installed updates and select from the list of updates.
File InformationSee Microsoft Knowledge Base Article 2743555
Registry Key VerificationNote A registry key does not exist to validate the presence of this update.

Deployment Information

Installing the Update

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

For more information about the terminology that appears in this bulletin, such as hotfix, see Microsoft Knowledge Base Article 824684.

This security update supports the following setup switches.

Supported Security Update Installation Switches
SwitchDescription
/?, /h, /helpDisplays help on supported switches.
/quietSuppresses the display of status or error messages.
/norestartWhen combined with /quiet, the system will not be restarted after installation even if a restart is required to complete installation.
/warnrestart:<seconds>When combined with /quiet, the installer will warn the user before initiating restart.
/promptrestartWhen combined with /quiet, the installer will prompt before initiating restart.
/forcerestartWhen combined with /quiet, the installer will forcefully close applications and initiate restart.
/log:<file name>Enables logging to specified file.
/extract:<destination>Extracts the package contents to the destination folder.
/uninstall /kb:<KB Number>Uninstalls the security update.

Note For more information about the wusa.exe installer, see "Windows Update Stand-alone Installer" in the TechNet article, Miscellaneous Changes in Windows 7.

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. See the section, Detection and Deployment Tools and Guidance, earlier in this bulletin for more information.

  • File Version Verification

    Because there are several editions of Microsoft Windows, the following steps may be different on your system. If they are, see your product documentation to complete these steps.

    1. Click Start and then enter an update file name in the Start Search box.
    2. When the file appears under Programs, right-click the file name and click Properties.
    3. On the General tab, compare the file size with the file information tables provided in the bulletin KB article.

      Note Depending on the edition of the operating system, or the programs that are installed on your system, some files that are listed in the file information table may not be installed.
    4. You can also click the Details tab and compare information, such as file version and date modified, with the file information tables provided in the bulletin KB article.

      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.
    5. Finally, you can also click the Previous Versions tab and compare file information for the previous version of the file with the file information for the new, or updated, version of the file.

Other Information

Microsoft Active Protections Program (MAPP)

To improve security protections for customers, Microsoft provides vulnerability information to major security software providers in advance of each monthly security update release. Security software providers can then use this vulnerability information to provide updated protections to customers via their security software or devices, such as antivirus, network-based intrusion detection systems, or host-based intrusion prevention systems. To determine whether active protections are available from security software providers, please go to the active protections websites provided by program partners, listed in Microsoft Active Protections Program (MAPP) Partners.

Support

How to obtain help and support for this security update

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 (October 9, 2012): Bulletin published.
  • V1.1 (May 29, 2013): Corrected update replacement entries in the Affected Software table for x64-based editions of Windows Server 2008 R2. This is a bulletin change only. There were no changes to detection logic or security update files.

Built at 2014-04-02T23:59:26Z-07:00

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