Security Bulletin

Microsoft Security Bulletin MS10-106 - Moderate

Vulnerability in Microsoft Exchange Server Could Allow Denial of Service (2407132)

Published: December 14, 2010

Version: 1.0

General Information

Executive Summary

This security update resolves a privately reported vulnerability in Microsoft Exchange Server. The vulnerability could allow denial of service if an authenticated attacker sent a specially crafted network message to a computer running the Exchange service. 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 Moderate for Microsoft Exchange Server 2007 Service Pack 2 for x64-based Systems. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerability by correcting the manner in which the Exchange Server store processes RPC 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 consider applying the security update 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, visit Microsoft Support Lifecycle.

Affected Software

Non-Affected Software

Frequently Asked Questions (FAQ) Related to This Security Update

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.

Does this update contain any non-security related changes to functionality? 
Yes. This update is released on the form of Update Rollup 5 for Exchange Server 2007 Service Pack 2, and as such includes all content provided by previous update rollups. No other changes aside from this security update are included in Update Rollup 5. For information about the contents of previous update rollups, see Microsoft Knowledge Base Article 981383.

Do I need to install the update rollup package for Exchange Server 2007-based servers in a particular sequence? 
Refer to the TechNet article, How to Install the Latest Service Pack or Update Rollup for Exchange 2007.

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, visit the Microsoft Support Lifecycle Web site.

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

Severity Ratings and Vulnerability Identifiers

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 December bulletin summary. For more information, see Microsoft Exploitability Index.

Exchange Server Infinite Loop Vulnerability - CVE-2010-3937

A denial of service vulnerability exists in the way that the Microsoft Exchange store processes specially crafted RPC calls. The vulnerable code path is only accessible to authenticated users. An authenticated attacker could exploit the vulnerability by sending a specially crafted network message to a computer running the Exchange service. An attacker who successfully exploited this vulnerability could cause the Exchange service to stop responding until manually restarted.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-3937.

Mitigating Factors for Exchange Server Infinite Loop Vulnerability - CVE-2010-3937

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.
• The vulnerable code path is only accessible to authenticated users. This vulnerability is not liable to be triggered if the attacker is not authenticated.

Workarounds for Exchange Server Infinite Loop Vulnerability - CVE-2010-3937

Microsoft has not identified any workarounds for this vulnerability.

FAQ for Exchange Server Infinite Loop Vulnerability - CVE-2010-3937

What is the scope of the vulnerability? 
This is a denial of service vulnerability. An attacker who exploited this vulnerability could cause the affected Exchange server service to stop responding until manually restarted. Note that the denial of service vulnerability would not allow an attacker to execute code or to elevate their user rights, but it could cause the affected system to stop accepting requests.

What causes the vulnerability? 
The vulnerability is caused when the Exchange Server store does not properly handle specially crafted RPC requests.

What is the Exchange Server store? 
The Exchange Server store is a storage platform that provides a single repository for managing multiple types of information in one infrastructure. The Exchange store has several logical components that interact with each other. These components can reside on a single server, or they can be distributed across multiple servers. For more information, see the TechNet article, Understanding the Exchange 2007 Store.

What is Remote Procedure Call (RPC)? 
Microsoft Remote Procedure Call (RPC) is an interprocess communication (IPC) mechanism that enables data exchange and invocation of functionality residing in a different process. That process can be on the same computer, on the local area network (LAN), or across the Internet. The Microsoft RPC mechanism uses other IPC mechanisms, such as named pipes, NetBIOS, or Winsock, to establish communications between the client and the server. With RPC, essential program logic and related procedure code can exist on different computers, which is important for distributed applications. For more information, see the TechNet article, What Is RPC?

Are all Exchange Server roles affected by this issue? 
No. Only Exchange servers that have the Mailbox Server role are affected by this issue. A server role is a unit that logically groups the required features and components that are required to perform a specific function in your messaging environment. Exchange servers may be configured to have multiple server roles that coexist on a single computer, or server roles may be deployed on dedicated computers. This issue affects the Mailbox Server role, so only systems deployed with this role are affected. However, this update will be offered to all affected Microsoft Exchange servers, regardless of what roles are configured on the system. For more information on server roles, see the TechNet article, Deploying Server Roles.

What is the Exchange Mailbox Server role? 
The Mailbox server role hosts mailbox databases, which contain users' mailboxes. If you plan to host user mailboxes, public folders, or both, the Mailbox server role is required. In Exchange Server 2007, the Mailbox server role integrates with the Active Directory directory service better than the mailbox features and functionality in earlier versions of Exchange. This improved integration makes deployment and operation tasks much easier. The Mailbox server role also improves the information worker experience by providing richer calendaring functionality, resource management, and offline address book downloads. For more information, see the TechNet article, Mailbox Server Role: Overview.

What might an attacker use the vulnerability to do? 
An attacker who successfully exploited this vulnerability could cause the MSExchangeIS service to stop responding until all Exchange services are manually restarted.

How could an attacker exploit the vulnerability? 
An attacker could exploit the vulnerability by creating a specially crafted RPC message and sending the message to an affected Exchange server over an affected TCP or UDP port. The vulnerable code path is only accessible to authenticated users. This vulnerability is not liable to be triggered if the attacker is not authenticated.

Which TCP or UDP ports are affected by this issue? 
This issue impacts RPC connections to the Exchange Mailbox server. Any TCP or UDP port configured to use RPC for these connections may be affected. To see the list of static ports and to determine which dynamic ports may be used in your environment, see the TechNet article, Understanding the Ports That are Used by Exchange 2007 in a Mixed Environment.

What systems are primarily at risk from the vulnerability? 
Exchange server systems are primarily at risk from this vulnerability.

What does the update do? 
The update addresses the vulnerability by correcting the manner in which the Exchange Server store processes RPC requests.

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

Detection and Deployment Tools and Guidance

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.

Security Update Deployment

Affected Software

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

Microsoft Exchange Server 2007

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.

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 Exchange hotfix.

For more information about the installer, visit the Microsoft TechNet Web site.

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.

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 Start Search.
  2. When the file appears under Programs, right-click on the file name and click Properties.
  3. Under 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 of the files that are listed in the file information table may not be installed.
  4. You may also click on 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 may also click on 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.

• Registry Key Verification

  You may also be able to verify the files that this security update has installed by reviewing the registry keys listed in the Reference Table in this section.

  These registry keys may not contain a complete list of installed files. Also, these registry keys may not be created correctly when an administrator or an OEM integrates or slipstreams this security update into the Windows installation source files.

Other Information

Acknowledgments

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

• Oleksandr Mirosh, working with TippingPoint's Zero Day Initiative, for reporting the Exchange Server Infinite Loop Vulnerability (CVE-2010-3937)

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 visit the active protections Web sites provided by program partners, listed in Microsoft Active Protections Program (MAPP) Partners.

Support

• Customers in the U.S. and Canada can receive technical support from Security Support or 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates. For more information about available support options, see Microsoft Help and Support.
• 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.

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 (December 14, 2010): Bulletin published.

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