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  Microsoft Virtual PC / Microsoft Virtual Server privilege escalation

From:MICROSOFT <secure_(at)_microsoft.com>
Date:15.07.2009
Subject:Microsoft Security Bulletin MS09-033 - Important Vulnerability in Virtual PC and Virtual Server Could Allow Elevation of Privilege (969856)

Microsoft Security Bulletin MS09-033 - Important
Vulnerability in Virtual PC and Virtual Server Could Allow Elevation of Privilege (969856)
Published: July 14, 2009

Version: 1.0
General Information
Executive Summary

This security update resolves a privately reported vulnerability in Microsoft Virtual PC and Microsoft Virtual Server. An attacker who successfully exploited this vulnerability could execute arbitrary code and take complete control of an affected guest operating system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

This security update is rated Important for all supported editions of Virtual PC 2004, Virtual PC 2007, and Virtual Server 2005. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerability by enforcing validation of privilege levels when executing machine instructions. 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. Microsoft recommends that customers apply the update at the earliest opportunity.

Known Issues. Microsoft Knowledge Base Article 969856 documents the currently known issues that customers may experience when installing this security update.
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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
Software Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by this Update

Microsoft Virtual PC 2004 Service Pack 1


Elevation of Privilege


Important


None

Microsoft Virtual PC 2007


Elevation of Privilege


Important


None

Microsoft Virtual PC 2007 Service Pack 1


Elevation of Privilege


Important


None

Microsoft Virtual PC 2007 x64 Edition


Elevation of Privilege


Important


None

Microsoft Virtual PC 2007 x64 Edition Service Pack 1


Elevation of Privilege


Important


None

Microsoft Virtual Server 2005 R2 Service Pack 1


Elevation of Privilege


Important


None

Microsoft Virtual Server 2005 R2 x64 Edition Service Pack 1


Elevation of Privilege


Important


None

Non-Affected Software
Software

Microsoft Virtual PC for Mac 7.1
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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.

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. To determine the support life cycle for your software release, visit Microsoft Support Lifecycle.

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. For more information about the Windows Product Lifecycle, visit Microsoft Support Lifecycle. For more information about the extended security update support period for these software versions or editions, visit Microsoft Product Support Services.

Customers who require custom support for older releases 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 Microsoft Worldwide Information, select the country, 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 Windows Operating System Product Support Lifecycle 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 July bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Virtual PC and Virtual Server Privileged Instruction Decoding Vulnerability - CVE-2009-1542 Aggregate Severity Rating

Microsoft Virtual PC 2004 Service Pack 1


Important
Elevation of Privilege


Important

Microsoft Virtual PC 2007 and Microsoft Virtual PC 2007 Service Pack 1


Important
Elevation of Privilege


Important

Microsoft Virtual PC 2007 x64 Edition and Microsoft Virtual PC 2007 x64 Edition Service Pack 1


Important
Elevation of Privilege


Important

Microsoft Virtual Server 2005 R2 Service Pack 1


Important
Elevation of Privilege


Important

Microsoft Virtual Server 2005 R2 x64 Edition Service Pack 1


Important
Elevation of Privilege


Important
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Virtual PC and Virtual Server Privileged Instruction Decoding Vulnerability - CVE-2009-1542

An elevation of privilege vulnerability exists in the way that Microsoft Virtual PC and Microsoft Virtual Server incorrectly validate privilege levels when executing specific instructions in the Virtual Machine Monitor. This vulnerability could allow an attacker to run code with elevated privileges inside the hosted guest operating system. An attacker could then install programs; view, change, or delete data; or create new accounts on the guest operating system with full user rights.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2009-1542.

Mitigating Factors for Virtual PC and Virtual Server Privileged Instruction Decoding Vulnerability - CVE-2009-1542

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 be authenticated and logged in to the guest operating system running in the virtual machine in order to exploit this vulnerability.


Windows Server 2008 Hyper-V is not affected by this vulnerability.


Windows Virtual PC and Windows XP Mode on Windows 7 are not affected by this vulnerability.


Deployments using Hardware Assisted Virtualization (HAV) are not affected by this vulnerability. HAV is supported by Virtual PC 2007 and Virtual Server 2005 R2 SP1, but on these versions HAV needs to be explicitly enabled.
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Workarounds for Virtual PC and Virtual Server Privileged Instruction Decoding Vulnerability - CVE-2009-1542

Microsoft has not identified any workarounds for this vulnerability.
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FAQ for Virtual PC and Virtual Server Privileged Instruction Decoding Vulnerability - CVE-2009-1542

What is the scope of the vulnerability?
This is an elevation of privilege vulnerability in Microsoft Virtual PC and Microsoft Virtual Server. An attacker who successfully exploited this vulnerability could execute arbitrary code and take complete control of a guest operating system hosted in a virtual machine by one of the affected products. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

What causes the vulnerability?
Virtual PC and Virtual Server do not correctly validate whether specific machine instructions require a minimum CPU privilege level in order to run within the guest operating system environment. This may allow user mode applications to execute instructions which should only be issued in kernel mode.

What are Microsoft Virtual PC and Virtual Server ?
Microsoft Virtual PC allows customers to create and run one or more virtual machines, each with its own operating system, on a single computer. It creates a virtualized environment that runs a guest operating system. Microsoft Virtual Server, on the other hand, is a similar solution for server operating systems.

What is the Virtual Machine Monitor (VMM)?
The Virtual Machine Monitor (VMM) component of Virtual Server 2005 is a kernel-mode driver running on the host operating system. VMM has limited and specific functionality, acting as a firewall between the host operating system and virtual machines. VMM has access to the physical computer processor and manages resources between the two environments, preventing malicious or poorly designed applications running in a guest operating system from requesting excessive hardware resources from the host operating system.

What is Hardware Assisted Virtualization (HAV)?
Hardware Assisted Virtualization is a technology that allows the processor to support the virtualization directly as opposed to virtualization being achieved entirely in software. HAV is available in processors that include a virtualization option; specifically, Intel VT or AMD Virtualization. Deployments configured to use Hardware Assisted Virtualization are not affected by this vulnerability.

Can this vulnerability be leveraged to compromise the host operating system?
No. This vulnerability can only allow elevation of privilege within the guest operating system. It does not allow an attacker to escape from the virtualized environment into the host operating system or any other guest operating systems hosted by the same Virtual Server or Virtual PC installation.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could run code with elevated privileges on the guest operating system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights on the guest operating system.

How could an attacker exploit the vulnerability?
To exploit this vulnerability, an attacker would first have to log on to the guest virtual machine. An attacker could then run a specially crafted application that could exploit the vulnerability and elevate privileges within the virtual machine environment.

What systems are primarily at risk from the vulnerability?
Guest operating systems hosting virtual machines that allow authenticated users to execute custom binaries are at the most risk from this vulnerability.

What does the update do?
The update addresses the vulnerability by enforcing validation of the required privilege levels when executing specific machine instructions on the guest operating system.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure. Microsoft had not received any information to indicate that this vulnerability had been publicly disclosed when this security bulletin was originally issued.

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 and had not seen any examples of proof of concept code published when this security bulletin was originally issued.

Other Information
Acknowledgments

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


Julien Tinnes and Tavis Ormandy of Google Inc. for reporting the Virtual PC and Virtual Server Privileged Instruction Decoding Vulnerability (CVE-2009-1542)
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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 (July 14, 2009): Bulletin published.

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