SecurityvulnsSECURITYVULNS:DOC:20745Microsoft Security Bulletin MS08-067 – Critical Vulnerability in Server Service Could Allow Remote Code Execution (958644)
Microsoft Security Bulletin MS08-067 – Critical
Vulnerability in Server Service Could Allow Remote Code Execution (958644)
Published: October 23, 2008
Version: 1.0
General Information
Executive Summary
This security update resolves a privately reported vulnerability in the Server service. The vulnerability could allow remote code execution if an affected system received a specially crafted RPC request. On Microsoft Windows 2000, Windows XP, and Windows Server 2003 systems, an attacker could exploit this vulnerability without authentication to run arbitrary code. It is possible that this vulnerability could be used in the crafting of a wormable exploit. Firewall best practices and standard default firewall configurations can help protect network resources from attacks that originate outside the enterprise perimeter.
This security update is rated Critical for all supported editions of Microsoft Windows 2000, Windows XP, Windows Server 2003, and rated Important for all supported editions of Windows Vista and Windows Server 2008. 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 Server service handles RPC requests. 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 immediately.
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
Microsoft Windows 2000 Service Pack 4
Remote Code Execution
Critical
MS06-040
Windows XP Service Pack 2
Remote Code Execution
Critical
MS06-040
Windows XP Service Pack 3
Remote Code Execution
Critical
None
Windows XP Professional x64 Edition
Remote Code Execution
Critical
MS06-040
Windows XP Professional x64 Edition Service Pack 2
Remote Code Execution
Critical
None
Windows Server 2003 Service Pack 1
Remote Code Execution
Critical
MS06-040
Windows Server 2003 Service Pack 2
Remote Code Execution
Critical
None
Windows Server 2003 x64 Edition
Remote Code Execution
Critical
MS06-040
Windows Server 2003 x64 Edition Service Pack 2
Remote Code Execution
Critical
None
Windows Server 2003 with SP1 for Itanium-based Systems
Remote Code Execution
Critical
MS06-040
Windows Server 2003 with SP2 for Itanium-based Systems
Remote Code Execution
Critical
None
Windows Vista and Windows Vista Service Pack 1
Remote Code Execution
Important
None
Windows Vista x64 Edition and Windows Vista x64 Edition Service Pack 1
Remote Code Execution
Important
None
Windows Server 2008 for 32-bit Systems*
Remote Code Execution
Important
None
Windows Server 2008 for x64-based Systems*
Remote Code Execution
Important
None
Windows Server 2008 for Itanium-based Systems
Remote Code Execution
Important
None
*Windows Server 2008 server core installation affected. For supported editions of Windows Server 2008, this update applies, with the same severity rating, whether or not 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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Frequently Asked Questions (FAQ) Related to This Security Update
Where are the file information details?
The file information details can be found in Microsoft Knowledge Base Article 958644.
Is the Windows 7 Pre-Beta release affected by this vulnerability?
Yes. This vulnerability was reported after the release of Windows 7 Pre-Beta. Customers running Windows 7 Pre-Beta are encouraged to download and apply the update to their systems. On Windows 7 Pre-Beta systems, the vulnerable code path is only accessible to authenticated users. This vulnerability is not liable to be triggered if the attacker is not authenticated, and therefore would be rated Important.
Security updates are available from Microsoft Update, Windows Update, and Office Update. Security updates are also available from the Microsoft Download Center. You can find them most easily by doing a keyword search for "security update."
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
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Server Service Vulnerability - CVE-2008-4250 Aggregate Severity Rating
Microsoft Windows 2000 Service Pack 4
Critical
Remote Code Execution
Critical
Windows XP Service Pack 2 and Windows XP Service Pack 3
Critical
Remote Code Execution
Critical
Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2
Critical
Remote Code Execution
Critical
Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2
Critical
Remote Code Execution
Critical
Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition Service Pack 2
Critical
Remote Code Execution
Critical
Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems
Critical
Remote Code Execution
Critical
Windows Vista and Windows Vista Service Pack 1
Important
Remote Code Execution
Important
Windows Vista x64 Edition and Windows Vista x64 Edition Service Pack 1
Important
Remote Code Execution
Important
Windows Server 2008 for 32-bit Systems*
Important
Remote Code Execution
Important
Windows Server 2008 for x64-based Systems*
Important
Remote Code Execution
Important
Windows Server 2008 for Itanium-based Systems
Important
Remote Code Execution
Important
*Windows Server 2008 server core installation affected. For supported editions of Windows Server 2008, this update applies, with the same severity rating, whether or not 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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Server Service Vulnerability - CVE-2008-4250
A remote code execution vulnerability exists in the Server service on Windows systems. The vulnerability is due to the service not properly handling specially crafted RPC requests. An attacker who successfully exploited this vulnerability could take complete control of an affected system.
To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2008-4250.
Mitigating Factors for Server Service Vulnerability - CVE-2008-4250
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:
•
Firewall best practices and standard default firewall configurations can help protect network resources from attacks that originate outside the enterprise perimeter. Best practices recommend that systems that are connected to the Internet have a minimal number of ports exposed.
•
On Windows Vista and Windows Server 2008, the vulnerable code path is only accessible to authenticated users. This vulnerability is not liable to be triggered if the attacker is not authenticated.
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Workarounds for Server Service Vulnerability - CVE-2008-4250
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:
•
Disable the Server and Computer Browser services
Disabling the Computer Browser and Server service on the affected systems will help protect systems from remote attempts to exploit this vulnerability.
You can disable these services by using the following steps:
Click Start, and then click Control Panel (or point to Settings and then click Control Panel).
Double-click Administrative Tools.
Double-click Services.
Double-click Computer Browser Service.
In the Startup type list, click Disabled.
Click Stop, and then click OK.
Repeat steps 4-6 for the Server service
Impact of Workaround. If the Computer Browser service is disabled, any services that explicitly depend on the Computer Browser service may log an error message in the system event log. For more information about the Computer Browser service, see Microsoft Knowledge Base Article 188001. If the Server service is disabled, you will not be able to share files or printers from your computer. However, you will still be able to view and use file shares and printer resources on other systems.
How to undo the workaround. You can enable these services by using the following steps:
Click Start, and then click Control Panel (or point to Settings, and then click Control Panel).
Double-click Administrative Tools.
Double-click Services.
Double-click Computer Browser Service.
In the Startup type list, click Automatic.
Click Start, and then click OK.
Repeat steps 4-6 for the Server service
•
On Windows Vista and Windows Server 2008, filter the affected RPC identifier
In addition to blocking ports with the Windows Firewall, the Windows Vista and Windows Server 2008 editions can selectively filter RPC Universally Unique Identifiers (UUID). To prevent this vulnerability, add a rule that blocks all RPC requests with the UUID equal to 4b324fc8-1670-01d3-1278-5a47bf6ee188. This is accomplished through the network shell. To access the network shell, run the following command from an elevated command prompt:
netsh
Once in the netsh environment, enter the following commands:
netsh>rpc
netsh rpc>filter
netsh rpc filter>add rule layer=um actiontype=block
netsh rpc filter>add condition field=if_uuid matchtype=equal data=4b324fc8-1670-01d3-1278-5a47bf6ee188
netsh rpc filter>add filter
netsh rpc filter>quit
The Filter Key is a randomly generated UUID specific to each system. To confirm the filter is in place, run the following command from an elevated command prompt:
netsh rpc filter show filter
If the commands are successful, the system displays the following information:
Listing all RPC Filters.
filterKey: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
displayData.name: RPCFilter
displayData.description: RPC Filter
filterId: 0x12f79
layerKey: um
weight: Type: FWP_EMPTY Value: Empty
action.type: block
numFilterConditions: 1
Where filterKey: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx equates to the randomly generated UUID relevant to your system.
Impact of workaround. Certain applications that rely on the Microsoft Server Message Block (SMB) Protocol may not function as intended. However, you will still be able to view and use file shares and printer resources on other systems.
How to undo the workaround. Run the following command from an elevated command prompt:
netsh rpc filter delete filter xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
Where filterKey: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx equates to the randomly generated UUID relevant to your system.
•
Block TCP ports 139 and 445 at the firewall
These ports are used to initiate a connection with the affected component. Blocking TCP ports 139 and 445 at the firewall will help protect systems that are behind that firewall from attempts to exploit this vulnerability. Microsoft recommends that you block all unsolicited inbound communication from the Internet to help prevent attacks that may use other ports. For more information about ports, see TCP and UDP Port Assignments.
Impact of workaround. Several Windows services use the affected ports. Blocking connectivity to the ports may cause various applications or services to not function. Some of the applications or services that could be impacted are listed below:
•
Applications that use SMB (CIFS)
•
Applications that use mailslots or named pipes (RPC over SMB)
•
Server (File and Print Sharing)
•
Group Policy
•
Net Logon
•
Distributed File System (DFS)
•
Terminal Server Licensing
•
Print Spooler
•
Computer Browser
•
Remote Procedure Call Locator
•
Fax Service
•
Indexing Service
•
Performance Logs and Alerts
•
Systems Management Server
•
License Logging Service
•
To help protect from network-based attempts to exploit this vulnerability, use a personal firewall, such as the Internet Connection Firewall
All supported editions of Windows Vista come with Windows Firewall, a two-way firewall that is automatically enabled.
For all supported editions of Windows XP and Windows Server 2003, use the Internet Connection Firewall feature to help protect your Internet connection by blocking unsolicited incoming traffic. Microsoft recommends that you block all unsolicited incoming communication from the Internet. In Windows XP Service Pack 2 and Windows XP Service Pack 3, this feature is called the Windows Firewall.
By default, the Windows Firewall feature in Windows XP helps protect your Internet connection by blocking unsolicited incoming traffic. We recommend that you block all unsolicited incoming communication from the Internet.
To enable the Windows Firewall feature by using the Network Setup Wizard, follow these steps:
Click Start, and then click Control Panel.
Double-click Network Connections and then click Change Windows Firewall Settings.
On the General tab, ensure that the On (recommended) value is selected. This will enable the Windows Firewall.
Once the Windows Firewall is enabled, select Don’t allow exceptions to prohibit all incoming traffic.
For Windows Server 2003 systems, configure Internet Connection Firewall manually for a connection using the following steps:
Click Start, and then click Control Panel.
In the default Category View, click Networking and Internet Connections, and then click Network Connections.
Right-click the connection on which you want to enable Internet Connection Firewall, and then click Properties.
Click the Advanced tab.
Click to select the Protect my computer or network by limiting or preventing access to this computer from the Internet check box, and then click OK.
Note If you want to enable certain programs and services to communicate through the firewall, click Settings on the Advanced tab, and then select the programs, the protocols, and the services that are required.
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FAQ for Server Service Vulnerability - CVE-2008-4250
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could take complete control of an affected system remotely. On Microsoft Windows 2000, Windows XP, and Windows Server 2003 systems, an attacker could exploit this vulnerability over RPC without authentication to run arbitrary code. It is possible that this vulnerability could be used in the crafting of a wormable exploit. If successfully exploited, an attacker could then install programs or view, change, or delete data; or create new accounts with full user rights.
What causes the vulnerability?
The vulnerability is caused by the Windows Server service not properly handling specially crafted RPC requests.
What is the Server service?
The Server service provides RPC support, file and print support, and named pipe sharing over the network. The Server service allows the sharing of your local resources (such as disks and printers) so that other users on the network can access them. It also allows named pipe communication between applications running on other computers and your computer, which is used for RPC.
What is RPC?
Remote Procedure Call (RPC) is a protocol that a program can use to request a service from a program located on another computer in a network. RPC helps with interoperability because the program using RPC does not have to understand the network protocols that are supporting communication. In RPC, the requesting program is the client and the service-providing program is the server.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take complete control of the affected system.
How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by sending a specially crafted message to an affected system. On Microsoft Windows 2000, Windows XP, and Windows Server 2003 systems, any anonymous user with access to the target network could deliver a specially crafted network packet to the affected system in order to exploit this vulnerability. On Windows Vista and Windows Server 2008 systems, however, only an authenticated user with access to the target network could deliver a specially crafted network packet to the affected system in order to exploit this vulnerability.
What systems are primarily at risk from the vulnerability?
While all workstations and servers are at risk regarding this issue, systems running Microsoft Windows 2000, Windows XP, or Windows Server 2003 are primarily at risk due to the unique characteristics of the vulnerability and affected code path.
What does the update do?
The update addresses the vulnerability by correcting the manner in which the Server service handles RPC requests.
When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
Yes. Microsoft is aware of limited, targeted attacks attempting to exploit the vulnerability. However, when the security bulletin was released, Microsoft had not seen any examples of proof of concept code published.
Does applying this security update help protect customers from the code that attempts to exploit this vulnerability?
Yes. This security update addresses the vulnerability that is currently being exploited. The vulnerability that has been addressed has been assigned the Common Vulnerability and Exposure number CVE-2008-4250.
Other Information
Support
•
Customers in the U.S. and Canada can receive technical support from Microsoft Product Support Services at 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates.
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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 (October 23, 2008): Bulletin published.
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