Security Bulletin

Microsoft Security Bulletin MS13-092 - Important

Vulnerability in Hyper-V Could Allow Elevation of Privilege (2893986)

Published: November 12, 2013

Version: 1.0

General Information

Executive Summary

This security update resolves a privately reported vulnerability in Microsoft Windows. The vulnerability could allow elevation of privilege if an attacker passes a specially crafted function parameter in a hypercall from an existing running virtual machine to the hypervisor. The vulnerability could also allow denial of service for the Hyper-V host if the attacker passes a specially crafted function parameter in a hypercall from an existing running virtual machine to the hypervisor.

This security update is rated Important for Windows 8 for x64-based Systems and Windows Server 2012. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerability by ensuring that Hyper-V properly sanitizes user input. 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.

Knowledge Base Article

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, see Microsoft Support Lifecycle.

Affected Software 

Non-Affected Software

Update FAQ

I do not have Hyper-V enabled. Can I install this update?
No. The update can only be installed on affected operating systems with Hyper-V enabled. Systems without Hyper-V enabled are not affected by the vulnerability.

Will this update be offered even if I do not have Hyper-V enabled?
This update will only be offered through automatic updating if Hyper-V is enabled. This applies whether or not the affected operating system was installed using the Server Core installation option.

Does this update need to be applied to Hyper-V guest virtual machines?
No. This update must not be applied to Hyper-V guest machines, but only to the servers that have Hyper-V enabled. The update will be offered through automatic updating only to the Hyper-V server system; it will not be offered within the virtualized guest machines.

What is Hyper-V?
Hyper-V is a hypervisor-based technology that is a key feature of Windows Server 2008, Windows Server 2008 R2, Windows 8, Windows Server 2012, Windows 8.1, and Windows Server 2012 R2. It provides a scalable, reliable, and highly available virtualization platform. This type of environment is useful because you can create and manage virtual machines, which allows you to run multiple operating systems on one physical computer and isolate the operating systems from each other.

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 2012 is affected by this vulnerability. The update must be applied to Hyper-V Server in order to be protected from the vulnerability described in this bulletin. Customers who have automatic updating enabled will automatically be offered the update 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 has 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

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

Address Corruption Vulnerability - CVE-2013-3898

An elevation of privilege vulnerability exists in Hyper-V on Windows 8 and Windows Server 2012. An attacker who successfully exploited this vulnerability could execute arbitrary code as System in another virtual machine (VM) on the shared Hyper-V host. An attacker would not be able to execute code on the Hyper-V host, only on guest VMs on the same host. The vulnerability could also allow denial of service in Hyper-V on the same platforms, allowing an attacker to cause the Hyper-V host to stop responding or restart.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2013-3898.

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

FAQ

What is the scope of the vulnerability?
This is an elevation of privilege vulnerability that could also be used to cause denial of service.

What causes the vulnerability?
The vulnerability is caused when the value of a data structure is not properly verified, allowing a memory address with an invalid address to be used.

Could an attacker take control of the Hyper-V host?
No. The Hyper-V host is not vulnerable to elevation of privilege.

Are only the guest VMs vulnerable?
No. While only the guest VMs are vulnerable to elevation of privilege, the Hyper-V host is vulnerable to denial of service attack from any of the running guest VMs. The denial of service would also impact all other VMs on the host, making them unavailable until the server is restarted.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could cause the Hyper-V host to crash, subsequently causing the guest VMs to crash as well. An attacker could also potentially execute code on another guest VM. For this to be possible, the target VM must be on the same host as the VM from which the attacker is operating.

How could an attacker exploit the vulnerability?
An authenticated attacker with administrator privileges on the source VM could exploit this vulnerability by passing a specially crafted function parameter in a hypercall to the host hypervisor.

What systems are primarily at risk from the vulnerability?
Affected systems with Hyper-V enabled are primarily at risk from this vulnerability.

What does the update do?
The update addresses the vulnerability by ensuring that Hyper-V properly sanitizes user input.

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

Several resources are available to help administrators deploy security updates. 

• Microsoft Baseline Security Analyzer (MBSA) lets administrators scan local and remote systems for missing security updates and common security misconfigurations. 
• Windows Server Update Services (WSUS), Systems Management Server (SMS), and System Center Configuration Manager help administrators distribute security updates. 
• The Update Compatibility Evaluator components included with Application Compatibility Toolkit aid in streamlining the testing and validation of Windows updates against installed applications. 

For information about these and other tools that are available, see Security Tools for IT Pros. 

Security Update Deployment

Affected Software

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

Windows 8 (all editions)

Reference Table

The following table contains the security update information for this software.

Windows Server 2012 (all editions)

Reference Table

The following table contains the security update information for this software.

Other Information

Acknowledgments

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

• thinktecture (www.thinktecture.com) & ERNW (www.ernw.de; Felix Wilhelm) on behalf of Bundesamt für Sicherheit in der Informationstechnik (BSI, German Federal Office for Information Security) for reporting the Address Corruption Vulnerability (CVE-2013-3898)

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

• Help installing updates: Support for Microsoft Update
• Security solutions for IT professionals: TechNet Security Troubleshooting and Support
• Help protect your computer that is running Windows from viruses and malware: Virus Solution and Security Center
• Local support according to your country: International Support

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 (November 12, 2013): Bulletin published.

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