SecurityvulnsSECURITYVULNS:DOC:22302Microsoft Security Bulletin MS09-041 - Important Vulnerability in Workstation Service Could Allow Elevation of Privilege (971657)
Microsoft Security Bulletin MS09-041 - Important
Vulnerability in Workstation Service Could Allow Elevation of Privilege (971657)
Published: August 11, 2009
Version: 1.0
General Information
Executive Summary
This security update resolves a privately reported vulnerability in the Windows Workstation Service. The vulnerability could allow elevation of privilege if an attacker created a specially crafted RPC message and sent the message to an affected system. An attacker who successfully exploited this vulnerability could execute arbitrary code and 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. An attacker must have valid logon credentials to a vulnerable system in order to exploit this vulnerability. The vulnerability could not be exploited by anonymous users.
This security update is rated Important for all supported editions of Windows XP and Windows Server 2003, and Moderate 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 manner in which the Workstation service allocates and frees memory. 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 XP Service Pack 2 and Windows XP Service Pack 3
Elevation of Privilege
Important
None
Windows XP Professional x64 Edition Service Pack 2
Elevation of Privilege
Important
None
Windows Server 2003 Service Pack 2
Elevation of Privilege
Important
None
Windows Server 2003 x64 Edition Service Pack 2
Elevation of Privilege
Important
None
Windows Server 2003 with SP2 for Itanium-based Systems
Elevation of Privilege
Important
None
Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2
Denial of Service
Moderate
None
Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2
Denial of Service
Moderate
None
Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2*
Denial of Service
Moderate
None
Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2*
Denial of Service
Moderate
None
Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2
Denial of Service
Moderate
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.
Non-Affected Software
Operating System
Microsoft Windows 2000 Service Pack 4
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 August bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Workstation Service Memory Corruption Vulnerability - CVE-2009-1544 Aggregate Severity Rating
Windows XP Service Pack 2 and Windows XP Service Pack 3
Important
Elevation of Privilege
Important
Windows XP Professional x64 Edition Service Pack 2
Important
Elevation of Privilege
Important
Windows Server 2003 Service Pack 2
Important
Elevation of Privilege
Important
Windows Server 2003 x64 Edition Service Pack 2
Important
Elevation of Privilege
Important
Windows Server 2003 with SP2 for Itanium-based Systems
Important
Elevation of Privilege
Important
Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2
Moderate
Denial of Service
Moderate
Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2
Moderate
Denial of Service
Moderate
Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2*
Moderate
Denial of Service
Moderate
Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2*
Moderate
Denial of Service
Moderate
Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2
Moderate
Denial of Service
Moderate
*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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Workstation Service Memory Corruption Vulnerability - CVE-2009-1544
An elevation of privilege vulnerability exists in the Windows Workstation Service due to a possible "Double Free" condition occurring in the service. An attacker who successfully exploited this vulnerability could run arbitrary code with elevated privileges. 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-2009-1544.
Mitigating Factors for Workstation Service Memory Corruption Vulnerability - CVE-2009-1544
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 networks 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.
•
An attacker must have valid logon credentials to a vulnerable system in order to exploit this vulnerability. The vulnerability could not be exploited by anonymous users.
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Workarounds for Workstation Service Memory Corruption Vulnerability - CVE-2009-1544
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:
•
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:
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Applications that use SMB (CIFS)
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Applications that use mailslots or named pipes (RPC over SMB)
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Server (File and Print Sharing)
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Group Policy
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Net Logon
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Distributed File System (DFS)
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Terminal Server Licensing
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Print Spooler
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Computer Browser
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Remote Procedure Call Locator
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Fax Service
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Indexing Service
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Performance Logs and Alerts
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Systems Management Server
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License Logging Service
How to undo the workaround. Unblock TCP ports 139 and 445 at the firewall. For more information about ports, see TCP and UDP Port Assignments.
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FAQ for Workstation Service Memory Corruption Vulnerability - CVE-2009-1544
What is the scope of the vulnerability?
This is an elevation of privilege vulnerability. An attacker who successfully exploited this vulnerability could execute arbitrary code and 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.
What causes the vulnerability?
The Windows Workstation Service does not properly allocate and free memory when receiving specially crafted RPC messages.
What is the Workstation service?
The Workstation service is a Windows component that supports the routing of remote file and network print resource requests. Both local file system requests and remote file or print network requests are routed through the Workstation service. This service determines where the resource is located and then routes the request to the local file system or to the networking components. When the Workstation service is stopped, all requests are assumed to be local requests.
What is a "double free"condition?
A double free condition is a condition in which a program is caused to release or free allocated memory more than once. Releasing memory that has already been freed could lead to memory corruption. An attacker could add arbitrary code to memory that is then executed when the corruption occurs. This code could then be executed at a system level of privilege.
Typically, this vulnerability will cause a denial of service to occur. However, in some circumstances, code execution could occur. Because of the unique layout of the memory on each affected system, exploiting this vulnerability on a mass scale could be difficult.
What is Remote Procedure Call (RPC)?
Microsoft Remote Procedure Call (RPC) is an interprocess communication (IPC) mechanism that enables data exchange and invocation of functionality residing in a different process. That process can be on the same computer, on the local area network (LAN), or across the Internet. The Microsoft RPC mechanism uses other IPC mechanisms, such as named pipes, NetBIOS, or Winsock, to establish communications between the client and the server. With RPC, essential program logic and related procedure code can exist on different computers, which is important for distributed applications. For more information, see the TechNet article, What Is RPC?
Can I disable the Workstation service to prevent this attack from succeeding?
Disabling the Workstation service is not recommended as a workaround for this vulnerability. If the Workstation service is disabled, the system cannot connect to any shared file resources or shared print resources on a network. Only use this workaround on stand-alone systems (such as many home systems) that do not connect to a network. If the Workstation service is disabled, any services that explicitly depend on the Workstation service do not start, and an error message is logged in the system event log. The following services depend on the Workstation service:
•
Alerter
•
Browser
•
Messenger
•
Net Logon
•
RPC Locator
These services are required to access resources on a network and to perform domain authentication. Internet connectivity and browsing for stand-alone systems, such as users on dial-up connections, on DSL connections, or on cable modem connections, should not be affected if these services are disabled.
Note: The Microsoft Baseline Security Analyzer will not function if the Workstation service is disabled.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could run arbitrary code with elevated privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.
How could an attacker exploit the vulnerability?
An attacker could exploit the vulnerability by creating a specially crafted RPC message and sending the message to an affected system. The message could then allow an authenticated client to write arbitrary data to memory in the Workstation service address space.
What systems are primarily at risk from the vulnerability?
All systems with the Workstation service enabled are at risk.
What does the update do?
The update addresses the vulnerability by correcting the manner in which the Workstation service allocates and frees memory.
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:
•
Cody Pierce of TippingPoint DVLabs for reporting the Workstation Service Memory Corruption Vulnerability (CVE-2009-1544)
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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
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V1.0 (August 11, 2009): Bulletin published.
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