Microsoft Security Bulletin MS10-010 - Important Vulnerability in Windows Server 2008 Hyper-V Could Allow Denial of Service (977894)

Microsoft Security Bulletin MS10-010 - Important
Vulnerability in Windows Server 2008 Hyper-V Could Allow Denial of Service (977894)
Published: February 09, 2010

Version: 1.0
General Information
Executive Summary

This security update resolves a privately reported vulnerability in Windows Server 2008 Hyper-V and Windows Server 2008 R2 Hyper-V. The vulnerability could allow denial of service if a malformed sequence of machine instructions is run by an authenticated user in one of the guest virtual machines hosted by the Hyper-V server. An attacker must have valid logon credentials and be able to log on locally into a guest virtual machine to exploit this vulnerability. The vulnerability could not be exploited remotely or by anonymous users.

This security update is rated Important for all supported x64-based editions of Windows Server 2008 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 the way Hyper-V server validates encoding on machine instructions executed inside its guest virtual machines. 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
Top of sectionTop of section
Affected and Non-Affected Software

The following software has 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
Operating System Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by this Update

Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2*

Denial of Service

Important

None

Windows Server 2008 R2 for x64-based Systems*

Denial of Service

Important

None

*Server Core installation affected. This update applies, with the same severity rating, to supported editions of Windows Server 2008 or Windows Server 2008 R2 as indicated, whether or not installed using the Server Core installation option. For more information on this installation option, see the MSDN articles, Server Core and Server Core for Windows Server 2008 R2. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008 and Windows Server 2008 R2; see Compare Server Core Installation Options.

Non-Affected Software
Operating System

Microsoft Windows 2000 Service Pack 4

Windows XP Service Pack 2 and 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, Windows Vista Service Pack 1, and Windows Vista Service Pack 2

Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2

Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2

Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2

Windows 7 for 32-bit Systems

Windows 7 for x64-based Systems

Windows Server 2008 R2 for Itanium-based Systems
Top of sectionTop of section

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.

Will this update be offered even if I do not have Hyper-V enabled?
This update can be installed manually on affected platforms even if the Hyper-V role is not enabled. However, the update will only be offered through Automatic Updates if the Hyper-V role is enabled.

Does this update need to be applied to Hyper-V guest virtual machines?
This update must not be applied to Hyper-V guest machines, but only to the machine that has the Hyper-V role enabled. It will be offered through Automatic Updates only to the Hyper-V server system and not inside the virtualized guest machines.

What is Hyper-V Server and is it also affected by this vulnerability?
Microsoft Hyper-V Server is a stand-alone product that provides a reliable and optimized virtualization solution enabling organizations to improve server utilization and reduce costs. Since Hyper-V Server is a dedicated stand-alone product, which contains only the Windows Hypervisor, Windows Server driver model and virtualization components, it provides a small footprint and minimal overhead.

Microsoft Hyper-V Server 2008, Microsoft Hyper-V Server 2008 Service Pack 2 and Microsoft Hyper-V Server 2008 R2 are affected by this vulnerability and the Windows Server 2008 and Windows Server 2008 R2 updates respectively must be applied to help remedy this vulnerability. Customers that have Automatic Updates enabled will automatically be offered these updates for installation.

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.
Top of sectionTop of section
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 February bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Hyper-V Instruction Set Validation Vulnerability - CVE-2010-0026 Aggregate Severity Rating

Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2*

Important
Denial of Service

Important

Windows Server 2008 R2 for x64-based Systems*

Important
Denial of Service

Important

*Server Core installation affected. This update applies, with the same severity rating, to supported editions of Windows Server 2008 or Windows Server 2008 R2 as indicated, whether or not installed using the Server Core installation option. For more information on this installation option, see the MSDN articles, Server Core and Server Core for Windows Server 2008 R2. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008 and Windows Server 2008 R2; see Compare Server Core Installation Options.
Top of sectionTop of section

Hyper-V Instruction Set Validation Vulnerability - CVE-2010-0026

A denial of service vulnerability exists in Hyper-V on Windows Server 2008 and Windows Server 2008 R2. The vulnerability is due to insufficient validation of specific sequences of machine instructions by Hyper-V. An attacker who successfully exploited this vulnerability could cause the affected Hyper-V system to stop responding. This would affect all virtual machines hosted by that system.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-0026.

Mitigating Factors for Hyper-V Instruction Set Validation Vulnerability - CVE-2010-0026

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:
•

An attacker must have valid logon credentials and be able to log on locally to a Hyper-V virtual machine to exploit this vulnerability. The vulnerability could not be exploited remotely or by anonymous users.
Top of sectionTop of section

Workarounds for Hyper-V Instruction Set Validation Vulnerability - CVE-2010-0026

Microsoft has not identified any workarounds for this vulnerability.
Top of sectionTop of section

FAQ for Hyper-V Instruction Set Validation Vulnerability - CVE-2010-0026

What is the scope of the vulnerability?
This is a denial of service vulnerability. An attacker who exploited this vulnerability could cause the affected Hyper-V server to stop responding and require it to be 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?
This vulnerability is caused by Hyper-V server incorrectly validating the encoding of specific machine instructions executed inside the guest virtual machines. Due to this lack of validation, processing of these instructions may cause the Hyper-V server application to become non-responsive.

What is Hyper-V?
Hyper-V is a hypervisor-based technology that is a key feature of Windows Server 2008 and Windows Server 2008 R2. It provides a scalable, reliable, and highly available virtualization platform. A virtualization environment is useful because users can create and manage virtual machines, allowing them to run multiple operating systems on one physical computer and isolate the operating systems from each other.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could cause a user’s system to become non-responsive until the system is restarted. Note that exploitation of this vulnerability could cause the actual Hyper-V server to stop responding, including all guest virtual machines hosted by that server.

How could an attacker exploit the vulnerability?
An attacker would have to be an authenticated user in one of the guest virtual machines hosted by the Hyper-V server and would need to have the ability to execute arbitrary code on the system. An attacker could then run an untrusted executable on the system that invokes a malformed sequence of machine instructions and thereby cause the Hyper-V server to become non-responsive.

What systems are primarily at risk from the vulnerability?
Hyper-V servers that host guest virtual machines which allow access to untrusted users are at particular risk of this vulnerability.

What does the update do?
The update addresses the vulnerability by correcting the way Hyper-V server validates encoding on machine instructions executed inside its guest virtual machines.

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

Other Information
Acknowledgments

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

Jan Bottorff for reporting the Hyper-V Instruction Set Validation Vulnerability (CVE-2010-0026)
Top of sectionTop of section
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 (February 9, 2010): Bulletin published.