Uočen je propust programskog paketa Hyper-V na operacijskom sustavu Windows Server 2008 koji zlonamjernim korisnicima omogućuje pokretanje napada uskraćivanja usluge (DoS).

Microsoft Security Bulletin MS11-047 - Important
Vulnerability in Hyper-V Could Allow Denial of Service (2525835)
Published: June 14, 2011

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 specially crafted packet is sent to the VMBus 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 send specially crafted content from 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 that the Hyper-V Server processes malformed requests from 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
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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
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
	

MS10-102

Windows Server 2008 R2 for x64-based Systems*
	

Denial of Service
	

Important
	

MS10-102

Windows Server 2008 R2 for x64-based Systems Service Pack 1*
	

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 TechNet articles, Managing a Server Core Installation and Servicing a Server Core Installation. 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

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 1 and Windows Vista Service Pack 2

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 and Windows 7 for 32-bit Systems Service Pack 1

Windows 7 for x64-based Systems and Windows 7 for x64-based Systems Service Pack 1

Windows Server 2008 R2 for Itanium-based Systems and Windows Server 2008 R2 for Itanium-based Systems Service Pack 1
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Frequently Asked Questions (FAQ) Related to This Security Update

I do not have Hyper-V enabled. Can I install this update? 
No. The update can only be installed on affected operating systems with the Hyper-V role enabled. Systems without the Hyper-V role 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 the Hyper-V role 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? 
This update must not be applied to Hyper-V guest machines, but only to the servers that have the Hyper-V role enabled. It will be offered through automatic updating 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. The respective Windows Server 2008 and Windows Server 2008 R2 updates must be applied to help remedy this vulnerability. Customers who have automatic updating enabled will automatically be offered these updates for 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.

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.
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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 June bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software	VMBus Persistent DoS Vulnerability - CVE-2011-1872	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 and Windows Server 2008 R2 for x64-based Systems Service Pack 1*
	

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 TechNet articles, Managing a Server Core Installation and Servicing a Server Core Installation. 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.
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VMBus Persistent DoS Vulnerability - CVE-2011-1872

A denial of service vulnerability exists in Hyper-V on Windows Server 2008 and Windows Server 2008 R2. The vulnerability is due to Hyper-V servers insufficiently validating specific sequences of machine instructions. 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-2011-1872.
	
Mitigating Factors for VMBus Persistent DoS Vulnerability - CVE-2011-1872

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:
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