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  Microsoft Windows SMB/CIFS service multiple security vulnerabilities

From:MICROSOFT <secure_(at)_microsoft.com>
Date:11.08.2010
Subject:Microsoft Security Bulletin MS10-054 - Critical Vulnerabilities in SMB Server Could Allow Remote Code Execution (982214)

Microsoft Security Bulletin MS10-054 - Critical
Vulnerabilities in SMB Server Could Allow Remote Code Execution (982214)
Published: August 10, 2010

Version: 1.0
General Information
Executive Summary

This security update resolves several privately reported vulnerabilities in Microsoft Windows. The most severe of these vulnerabilities could allow remote code execution if an attacker created a specially crafted SMB packet and sent the packet to an affected system. Firewall best practices and standard default firewall configurations can help protect networks from attacks originating outside the enterprise perimeter that would attempt to exploit these vulnerabilities.

This security update is rated Critical for all supported editions of Windows XP and Important for all supported editions of Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses these vulnerabilities by correcting the way that SMB validates SMB requests. For more information about the vulnerabilities, 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 XP Service Pack 3


Remote Code Execution


Critical


MS10-012

Windows XP Professional x64 Edition Service Pack 2


Remote Code Execution


Critical


MS10-012

Windows Server 2003 Service Pack 2


Remote Code Execution


Important


MS10-012

Windows Server 2003 x64 Edition Service Pack 2


Remote Code Execution


Important


MS10-012

Windows Server 2003 with SP2 for Itanium-based Systems


Remote Code Execution


Important


MS10-012

Windows Vista Service Pack 1 and Windows Vista Service Pack 2


Elevation of Privilege


Important


MS10-012

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


Elevation of Privilege


Important


MS10-012

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


Elevation of Privilege


Important


MS10-012

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


Elevation of Privilege


Important


MS10-012

Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2


Elevation of Privilege


Important


MS10-012

Windows 7 for 32-bit Systems


Remote Code Execution


Important


MS10-012

Windows 7 for x64-based Systems


Remote Code Execution


Important


MS10-012

Windows Server 2008 R2 for x64-based Systems*


Remote Code Execution


Important


MS10-012

Windows Server 2008 R2 for Itanium-based Systems


Remote Code Execution


Important


MS10-012

*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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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.

Why does this update address several reported security vulnerabilities?
This update contains support for several vulnerabilities because the modifications that are required to address these issues are located in related files. Instead of having to install several updates that are almost the same, customers need to install this update only.

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 August bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software SMB Pool Overflow Vulnerability - CVE-2010-2550 SMB Variable Validation Vulnerability - CVE-2010-2551 SMB Stack Exhaustion Vulnerability - CVE-2010-2552 Aggregate Severity Rating

Windows XP Service Pack 3


Critical
Remote Code Execution


Not applicable


Not applicable


Critical

Windows XP Professional x64 Edition Service Pack 2


Critical
Remote Code Execution


Not applicable


Not applicable


Critical

Windows Server 2003 Service Pack 2


Important
Remote Code Execution


Not applicable


Not applicable


Important

Windows Server 2003 x64 Edition Service Pack 2


Important
Remote Code Execution


Not applicable


Not applicable


Important

Windows Server 2003 with SP2 for Itanium-based Systems


Important
Remote Code Execution


Not applicable


Not applicable


Important

Windows Vista Service Pack 1 and Windows Vista Service Pack 2


Important
Elevation of Privilege


Important
Denial of Service


Important
Denial of Service


Important

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


Important
Elevation of Privilege


Important
Denial of Service


Important
Denial of Service


Important

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


Important
Elevation of Privilege


Important
Denial of Service


Important
Denial of Service


Important

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


Important
Elevation of Privilege


Important
Denial of Service


Important
Denial of Service


Important

Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2


Important
Elevation of Privilege


Important
Denial of Service


Important
Denial of Service


Important

Windows 7 for 32-bit Systems


Important
Remote Code Execution


Important
Denial of Service


Important
Denial of Service


Important

Windows 7 for x64-based Systems


Important
Remote Code Execution


Important
Denial of Service


Important
Denial of Service


Important

Windows Server 2008 R2 for x64-based Systems*


Important
Remote Code Execution


Important
Denial of Service


Important
Denial of Service


Important

Windows Server 2008 R2 for Itanium-based Systems


Important
Remote Code Execution


Important
Denial of Service


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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SMB Pool Overflow Vulnerability - CVE-2010-2550

An unauthenticated remote code execution vulnerability exists in the way that Microsoft Server Message Block (SMB) Protocol software handles specially crafted SMB packets. An attempt to exploit the vulnerability would not require authentication, allowing an attacker to exploit the vulnerability by sending a specially crafted network message to a computer running the Server service. An attacker who successfully exploited this vulnerability could take complete control of the system.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-2550.

Mitigating Factors for SMB Pool Overflow Vulnerability - CVE-2010-2550

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. In this case, the SMB ports should be blocked from the Internet.


In Windows Vista and Windows 7, if the network profile is set to "Public", the system is not affected by this vulnerability since unsolicited inbound network packets are blocked by default.
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Workarounds for SMB Pool Overflow Vulnerability - CVE-2010-2550

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 the TechNet article, 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

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 SMB Pool Overflow Vulnerability - CVE-2010-2550

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. 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 when the Microsoft Server Message Block (SMB) implementation improperly validates fields in a malformed SMB request.

What is Microsoft Server Message Block (SMB) Protocol?
Microsoft Server Message Block (SMB) Protocol is a Microsoft network file sharing protocol used in Microsoft Windows. For more information, see Microsoft SMB Protocol and CIFS Protocol Overview.

What is Microsoft Server Message Block Version 2 (SMBv2)?
Server Message Block (SMB) is the file sharing protocol used by default on Windows-based computers. SMB Version 2.0 (SMBv2) is an update to this protocol, and is only supported on computers running Windows Server 2008, Windows 7, and Windows Vista. SMBv2 can only be used if both client and server support it. If either client or server cannot support SMBv2, the SMB 1.0 protocol will be used instead. The SMB protocol version to be used for file operations is decided during the negotiation phase. During the negotiation phase, a Windows Vista client advertises to the server that the client can understand the new SMBv2 protocol. If the server (Windows Server 2008 or later) understands SMBv2, then SMBv2 is chosen for subsequent communication. Otherwise the client and server use SMB 1.0 and continue to function as normal. For more information on SMBv2, see the MSDN article, Server Message Block (SMB) Version 2 Protocol Specification.

What is the difference between SMBv1 and SMBv2?
Both protocols are used by clients to request file and print services from a server system over the network. Both are stateful protocols in which clients establish a connection to a server, establish an authenticated context on that connection, and then issue a variety of requests to access files, printers, and named pipes for inter-process communication. The SMBv2 protocol is a major revision of the existing SMB protocol. While many of the underlying concepts are the same, the packet formats are completely different. In addition to providing all of the capabilities found in SMBv1, the SMBv2 protocol provides several enhancements:


Allowing a session with an open file to be reestablished after a client connection becomes temporarily disconnected.


Allowing the server to balance the number of simultaneous operations that a client can have outstanding at any time.


Providing scalability in terms of the number of shares, users, and simultaneously open files.


Supporting symbolic links.


Using a stronger algorithm to validate the integrity of requests and responses.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take complete control of an affected system.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by creating a specially crafted SMB packet and sending the packet to an affected system. On Windows Vista, Windows Server 2008, Windows 7, and Windows 2008 R2 platforms, an attacker must be authenticated in order to exploit this vulnerability unless password-based sharing is disabled. If password-based sharing is disabled, attackers could exploit these platforms without authentication.

What systems are primarily at risk from the vulnerability?
All systems with SMB Server service are affected by this vulnerability. Domain controllers are at a greater risk from exploitation of this vulnerability, as these systems have network shares open to all domain users by default.

What does the update do?
The update addresses the vulnerability by correcting the manner in which SMB validates fields in a malformed SMB request.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through coordinated vulnerability 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 when this security bulletin was originally issued.
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SMB Variable Validation Vulnerability - CVE-2010-2551

A denial of service vulnerability exists in the way that Microsoft Server Message Block (SMB) Protocol software handles specially crafted SMB packets. An attempt to exploit the vulnerability would not require authentication, allowing an attacker to exploit the vulnerability by sending a specially crafted network message to a computer running the Server service.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-2551.

Mitigating Factors for SMB Variable Validation Vulnerability - CVE-2010-2551

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:


This vulnerability would not allow an attacker to execute code or elevate their user rights, but it could cause the affected system to stop responding until manually restarted.


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. In this case, the SMB ports should be blocked from the Internet.


In Windows Vista and Windows 7, if the network profile is set to "Public", the system is not affected by this vulnerability since unsolicited inbound network packets are blocked by default.
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Workarounds for SMB Variable Validation Vulnerability - CVE-2010-2551

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 the TechNet article, 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

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 SMB Variable Validation Vulnerability - CVE-2010-2551

What is the scope of the vulnerability?
This is a denial of service vulnerability. An attacker who exploited this vulnerability could cause the affected system to stop responding until it is manually restarted. Note that the denial of service vulnerability would not allow an attacker to execute code or to elevate their user rights, but it could cause the affected system to stop accepting requests.

What causes the vulnerability?
The vulnerability is caused when the Microsoft Server Message Block (SMB) Protocol software improperly validates an internal variable when parsing specially crafted SMB packets. This vulnerability affects SMB version 1 and SMB version 2.

What is Microsoft Server Message Block (SMB) Protocol?
Microsoft Server Message Block (SMB) Protocol is a Microsoft network file sharing protocol used in Microsoft Windows. For more information on SMB see Microsoft SMB Protocol and CIFS Protocol Overview.

What is Microsoft Server Message Block Version 2 (SMBv2)?
Server Message Block (SMB) is the file sharing protocol used by default on Windows-based computers. SMB Version 2.0 (SMBv2) is an update to this protocol, and is only supported on computers running Windows Server 2008, Windows 7, and Windows Vista. SMBv2 can only be used if both client and server support it. If either client or server cannot support SMBv2, the SMB 1.0 protocol will be used instead. The SMB protocol version to be used for file operations is decided during the negotiation phase. During the negotiation phase, a Windows Vista client advertises to the server that the client can understand the new SMBv2 protocol. If the server (Windows Server 2008 or later) understands SMBv2, then SMBv2 is chosen for subsequent communication. Otherwise the client and server use SMB 1.0 and continue to function as normal. For more information on SMBv2, see the MSDN article, Server Message Block (SMB) Version 2 Protocol Specification.

What is the difference between SMBv1 and SMBv2?
Both protocols are used by clients to request file and print services from a server system over the network. Both are stateful protocols in which clients establish a connection to a server, establish an authenticated context on that connection, and then issue a variety of requests to access files, printers, and named pipes for inter-process communication. The SMBv2 protocol is a major revision of the existing SMB protocol. While many of the underlying concepts are the same, the packet formats are completely different. In addition to providing all of the capabilities found in SMBv1, the SMBv2 protocol provides several enhancements:


Allowing a session with an open file to be reestablished after a client connection becomes temporarily disconnected.


Allowing the server to balance the number of simultaneous operations that a client can have outstanding at any time.


Providing scalability in terms of the number of shares, users, and simultaneously open files.


Supporting symbolic links.


Using a stronger algorithm to validate the integrity of requests and responses.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could cause a user's system to stop responding until manually restarted.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by creating a specially crafted SMB packet and sending the packet to an affected system.

What systems are primarily at risk from the vulnerability?
All systems with SMB Server service are affected by this vulnerability. Domain controllers are at a greater risk from exploitation of this vulnerability, as these systems have network shares open to all domain users by default.

What does the update do?
The security update addresses the vulnerability by correcting the manner in which SMB validates internal fields within specially crafted SMB packets.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through coordinated vulnerability 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 when this security bulletin was originally issued.
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SMB Stack Exhaustion Vulnerability - CVE-2010-2552

A denial of service vulnerability exists in the way that Microsoft Server Message Block (SMB) Protocol software handles specially crafted SMB compounded requests. An attempt to exploit the vulnerability would not require authentication, allowing an attacker to exploit the vulnerability by sending a specially crafted network message to a computer running the Server service.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-2552.

Mitigating Factors for SMB Stack Exhaustion Vulnerability - CVE-2010-2552

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. In this case, the SMB ports should be blocked from the Internet.


In Windows Vista and Windows 7, if the network profile is set to "Public", the system is not affected by this vulnerability since unsolicited inbound network packets are blocked by default.
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Workarounds for SMB Stack Exhaustion Vulnerability - CVE-2010-2552

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 the TechNet article, 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

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.


Disable SMB v2

Note See Microsoft Knowledge Base Article 975517 to use the automated Microsoft Fix it solution to enable or disable this workaround.

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.

1.


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

2.


Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services

3.


Click LanmanServer.

4.


Click Parameters.

5.


Right-click to add a new DWORD (32 bit) Value.

6.


Enter smb2 in the Name data field, and change the Value data field to 0.

7.


Exit.

8.


Restart the "Server" service by performing one of the following:

- Open up the computer management MMC, navigate to Services and Applications, click Services, right-click the Server service name and click Restart. Answer Yes in the pop-up menu.

- From a command prompt and with administrator privileges, type net stop server and then net start server.

Impact of workaround. The host will not communicate using SMBv2. Instead, the host will communicate using SMB 1.0. This should not impact basic services such as file and printer sharing. These will continue to function as normal.

How to undo the workaround:

1.


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

2.


Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services

3.


Click LanmanServer.

4.


Click Parameters.

5.


Double-click smb2, and change the Value data field to 1.

6.


Exit.

7.


Restart the "Server" service by performing one of the following:

- Open up the computer management MMC, navigate to Services and Applications, click Services, right-click the Server service name and click Restart. Answer Yes in the pop-up menu.

- From a command prompt and with administrator privileges, type net stop server and then net start server.
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FAQ for SMB Stack Exhaustion Vulnerability - CVE-2010-2552

What is the scope of the vulnerability?
This is a denial of service vulnerability. An attacker who exploited this vulnerability could cause the affected system to stop responding until it is manually restarted. Note that the denial of service vulnerability would not allow an attacker to execute code or to elevate their user rights, but it could cause the affected system to stop accepting requests.

What causes the vulnerability?
The vulnerability is caused when the Microsoft Server Message Block (SMB) Protocol software insufficiently handles specially crafted compounded requests.

What is Microsoft Server Message Block (SMB) Protocol?
Microsoft Server Message Block (SMB) Protocol is a Microsoft network file sharing protocol used in Microsoft Windows. For more information on SMB see Microsoft SMB Protocol and CIFS Protocol Overview.

What is Microsoft Server Message Block Version 2 (SMBv2)?
Server Message Block (SMB) is the file sharing protocol used by default on Windows-based computers. SMB Version 2.0 (SMBv2) is an update to this protocol, and is only supported on computers running Windows Server 2008, Windows 7, and Windows Vista. SMBv2 can only be used if both client and server support it. If either client or server cannot support SMBv2, the SMB 1.0 protocol will be used instead. The SMB protocol version to be used for file operations is decided during the negotiation phase. During the negotiation phase, a Windows Vista client advertises to the server that the client can understand the new SMBv2 protocol. If the server (Windows Server 2008 or later) understands SMBv2, then SMBv2 is chosen for subsequent communication. Otherwise the client and server use SMB 1.0 and continue to function as normal. For more information on SMBv2, see the MSDN article, Server Message Block (SMB) Version 2 Protocol Specification.

What is the difference between SMBv1 and SMBv2?
Both protocols are used by clients to request file and print services from a server system over the network. Both are stateful protocols in which clients establish a connection to a server, establish an authenticated context on that connection, and then issue a variety of requests to access files, printers, and named pipes for inter-process communication. The SMBv2 protocol is a major revision of the existing SMB protocol. While many of the underlying concepts are the same, the packet formats are completely different. In addition to providing all of the capabilities found in SMBv1, the SMBv2 protocol provides several enhancements:


Allowing a session with an open file to be reestablished after a client connection becomes temporarily disconnected.


Allowing the server to balance the number of simultaneous operations that a client can have outstanding at any time.


Providing scalability in terms of the number of shares, users, and simultaneously open files.


Supporting symbolic links.


Using a stronger algorithm to validate the integrity of requests and responses.

Does this issue affect Server Message Block Version 1 (SMBv1)?
No. This issue only affects SMBv2 as compounded requests are a new feature introduced in SMBv2.

What is an SMBv2 compounded request?
An SMBv2 compounded request is a method of combining multiple SMBv2 Protocol requests or responses into a single transmission request for submission to the underlying transport.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by creating a specially crafted SMB packet and sending the packet to an affected system.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could cause a user's system to stop responding until manually restarted.

What systems are primarily at risk from the vulnerability?
All systems with SMB Server service are affected by this vulnerability. Domain controllers are at a greater risk from exploitation of this vulnerability, as these systems have network shares open to all domain users by default.

What does the update do?
The security update addresses the vulnerability by correcting the manner in which the SMB protocol software handles malformed compounded requests.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through coordinated vulnerability 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 when this security bulletin was originally issued.

Other Information
Acknowledgments

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


Laurent Gaffié of stratsec for reporting the SMB Pool Overflow Vulnerability (CVE-2010-2550)


Todd Wease and Richard Johnson of Sourcefire VRT for reporting the SMB Stack Exhaustion Vulnerability (CVE-2010-2552)


Riku Hietamaki and Joshua Morin of Codenomicon for reporting the SMB Stack Exhaustion Vulnerability (CVE-2010-2552)
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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 (August 10, 2010): Bulletin published.

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