Microsoft Security Bulletin MS11-005 - ImportantVulnerability in Active Directory Could Allow Denial of Service (2478953)Published: February 08, 2011 Version: 1.0 General InformationExecutive SummaryThis security update resolves a publicly disclosed vulnerability in Active Directory. The vulnerability could allow denial of service if an attacker sent a specially crafted packet to an affected Active Directory server. The attacker must have valid local administrator privileges on the domain-joined computer in order to exploit this vulnerability. This security update is rated Important for Active Directory on all supported editions of Windows Server 2003. For more information, see the subsection, Affected and Non-Affected Software, in this section. The security update addresses the vulnerability by correcting the way that the Active Directory server handles service principal name (SPN) update requests. 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. The majority of 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 SoftwareThe 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, visit Microsoft Support Lifecycle. Affected Software
Non-Affected Software
I am running one of the platforms that are listed in the Affected Software table. Why am I not being offered the update? Where are the file information details? I am using an older release of the software discussed in this security bulletin. What should I do? 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 Lifecycle Supported Service Packs. 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, visit the Microsoft Worldwide Information Web site, 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 February bulletin summary. For more information, see Microsoft Exploitability Index.
A denial of service vulnerability exists in implementations of Microsoft Windows Active Directory due to improper validation of service principal names (SPN), which could result in SPN collisions. When this occurs, services that use the SPN will downgrade to NT LAN Manager (NTLM) if configured to negotiate. Services that are not configured to negotiate will become unavailable, resulting in a denial of service condition. An attacker who successfully exploited this vulnerability could cause the affected system to stop responding. To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2011-0040.
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:
Microsoft has not identified any workarounds for this vulnerability.
What is the scope of the vulnerability? What causes the vulnerability? What is Active Directory? What is SPN? What is NTLM? Interactive NTLM authentication over a network typically involves two systems: a client system, where the user is requesting authentication, and a domain controller, where information related to the user's password is kept. Non-interactive authentication, which may be required to permit an already logged-on user to access a resource such as a server application, typically involves three systems: a client, a server, and a domain controller that does the authentication calculations on behalf of the server. What is Kerberos? 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? How could an attacker exploit the vulnerability? What systems are primarily at risk from the vulnerability? What does the update do? When this security bulletin was issued, had this vulnerability been publicly disclosed? When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited? 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 Web site 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, "MS07-036"), you can add all of 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) allows administrators to scan local and remote systems for missing security updates as well as common security misconfigurations. For more information about MBSA, visit Microsoft Baseline Security Analyzer. The following table provides the MBSA detection summary for this security update.
Note For customers using legacy software not supported by the latest release of MBSA, Microsoft Update, and Windows Server Update Services, please visit 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.
For SMS 2.0 and SMS 2003, the Security Update Inventory Tool (SUIT) can be used by SMS to detect security updates. See also Downloads for Systems Management Server 2.0. 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 2007 uses WSUS 3.0 for detection of updates. For more information about Configuration Manager 2007 Software Update Management, visit System Center Configuration Manager 2007. For more information about SMS, visit the SMS Web site. 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 Microsoft 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:
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.
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. If you have previously installed a hotfix to update one of these files, the installer copies the RTMQFE, SP1QFE, or SP2QFE files to your system. Otherwise, the installer copies the RTMGDR, SP1GDR, or SP2GDR files to your system. Security updates may not contain all variations of these files. For more information about this behavior, see Microsoft Knowledge Base Article 824994. For more information about the installer, see Microsoft Knowledge Base Article 832475. 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.
Note You can combine these switches into one command. For backward compatibility, the security update also supports many of 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. Removing the Update This security update supports the following setup switches.
Verifying that the Update Has Been Applied
Other InformationMicrosoft 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 visit the active protections Web sites provided by program partners, listed in Microsoft Active Protections Program (MAPP) Partners. Support
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