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HistorySep 09, 2009 - 12:00 a.m.

Microsoft Security Bulletin MS09-049 - Critical Vulnerability in Wireless LAN AutoConfig Service Could Allow Remote Code Execution (970710)

2009-09-0900:00:00
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Microsoft Security Bulletin MS09-049 - Critical
Vulnerability in Wireless LAN AutoConfig Service Could Allow Remote Code Execution (970710)
Published: September 08, 2009

Version: 1.0
General Information
Executive Summary

This security update resolves a privately reported vulnerability in Wireless LAN AutoConfig Service. The vulnerability could allow remote code execution if a client or server with a wireless network interface enabled receives specially crafted wireless frames. Systems without a wireless card enabled are not at risk from this vulnerability.

This security update is rated Critical for supported editions of Windows Vista and Important for supported editions of Windows Server 2008. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerability by extending the Wireless LAN AutoConfig service to properly validate wireless frames prior to processing them. 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 immediately 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 Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2

Remote Code Execution

Critical

None

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

Remote Code Execution

Critical

None

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

Remote Code Execution

Important

None

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

Remote Code Execution

Important

None

*Windows Server 2008 Server Core installation not affected. The vulnerability addressed by this update does not affect supported editions of Windows Server 2008 if Windows Server 2008 was installed using the Server Core installation option. For more information on this installation option, see Server Core. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008; 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 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 x64-based Systems

Windows Server 2008 R2 for Itanium-based Systems
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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 September bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Wireless Frame Parsing Remote Code Execution Vulnerability - CVE-2009-1132 Aggregate Severity Rating

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

Critical
Remote Code Execution

Critical

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

Critical
Remote Code Execution

Critical

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

Important
Remote Code Execution

Important

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

Important
Remote Code Execution

Important

*Windows Server 2008 Server Core installation not affected. The vulnerability addressed by this update does not affect supported editions of Windows Server 2008 if Windows Server 2008 was installed using the Server Core installation option. For more information on this installation option, see Server Core. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008; see Compare Server Core Installation Options.
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Wireless Frame Parsing Remote Code Execution Vulnerability - CVE-2009-1132

A remote code execution vulnerability exists in the way that the Wireless LAN AutoConfig Service (wlansvc) parses specific frames received on the wireless network. This vulnerability could allow remote code execution if a client or server with a wireless network interface enabled receives specially crafted wireless frames. If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2009-1132.

Mitigating Factors for Wireless Frame Parsing Remote Code Execution Vulnerability - CVE-2009-1132

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:

Systems without a wireless card enabled are not at risk from this vulnerability.
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Workarounds for Wireless Frame Parsing Remote Code Execution Vulnerability - CVE-2009-1132

Workaround refers to a setting or configuration change that does not correct the underlying vulnerability but would help block known attack vectors before you apply the update. Microsoft has tested the following workarounds and states in the discussion whether a workaround reduces functionality:

Unregister Wlansvc

To modify the registry key, perform the following steps:

Note Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Using the Interactive Method

Click Start, click Run, type Regedit in the Open box, and then click OK.

Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services

Click Wlansvc.

Click the File menu and select Export.

In the Export Registry File dialog box, enter Wlansvc_configuration_backup.reg and click Save.

Note This will create a backup of this registry key in the My Documents folder by default.

Double-click the Start value and change the Value data field to 4.

Click OK.

Run the following command from a command prompt as an administrator:

sc stop Wlansvc

Using a Managed Deployment Script

Create a backup copy of the registry keys by using a managed deployment script that contains the following commands:

Regedit.exe /e Wlansvc_configuration_backup.reg
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Wlansvc

Next, save the following to a file with a .REG extension, such as Disable_Wlansvc.reg:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Wlansvc]
"Start"=dword:00000004

Run the above registry script on the target machine with the following command:

Regedit.exe /s Disable_Wlansvc.reg

Run the following command from a command prompt as an administrator:

sc stop Wlansvc

Impact of workaround. Wireless networking will not be available.

How to undo the workaround:

Using the Interactive Method

Click Start, click Run, type Regedit in the Open box, and then click OK.

Click the File menu and select Import.

In the Import Registry File dialog box, select Wlansvc_configuration_backup.reg and click Open.

Using a Managed Deployment Script

Restore the original state by running the following command:

Regedit.exe /s Wlansvc_configuration_backup.reg
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FAQ for Wireless Frame Parsing Remote Code Execution Vulnerability - CVE-2009-1132

What is the scope of the vulnerability?
This vulnerability affects Windows clients and servers that use wireless networking and are within the range of a wireless transmitter operated by an attacker. This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could take complete control of an affected system remotely. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

What causes the vulnerability?
The vulnerability is caused by lack of validation of part of a specific malformed frame transmitted by a remote wireless transmitter. This could lead to a heap overflow situation that may result in arbitrary code execution.

What is the Wireless LAN AutoConfig Service (Wlansvc)?
WLAN AutoConfig is a service that configures wireless security and connectivity settings. WLAN AutoConfig configures Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless adapters for connectivity to ad-hoc wireless networks, small-office wireless infrastructure networks, and for networks that provide 802.1x-authenticated network access. When enabled, WLAN AutoConfig settings apply to all IEEE 802.11 wireless network adapters that are installed on a computer.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts.

How could an attacker exploit the vulnerability?
An attacker could deploy a wireless transmitter that transmits maliciously crafted frames to trigger the vulnerability.

What systems are primarily at risk from the vulnerability?
All clients and servers with an enabled wireless network interface are at risk from this vulnerability.

What does the update do?
This security update resolves the vulnerability by extending the Wireless LAN AutoConfig service to properly validate wireless frames prior to processing them.

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

Other Information
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 (September 8, 2009): Bulletin published.

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