Security Bulletin
Microsoft Security Bulletin MS07-063 - Critical
Vulnerability in SMBv2 Could Allow Remote Code Execution (942624)
Published: December 11, 2007 | Updated: December 19, 2007
Version: 1.1
General Information
Executive Summary
This important security update resolves a privately reported vulnerability in Server Message Block Version 2 (SMBv2). The vulnerability could allow an attacker to tamper with data transferred via SMBv2, which could allow remote code execution in domain configurations communicating with SMBv2.
This is an Important security update for all supported versions of Windows Vista. For more information, see the subsection, Affected and Non-Affected Software, in this section.
This security update addresses the vulnerability by implementing proper signing using SMBv2. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section, Vulnerability Information.
Recommendation. Microsoft recommends that customers apply the update at the earliest opportunity.
Known Issues. None
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 | Remote Code Execution | Important | None |
| Windows Vista x64 | Remote Code Execution | Important | None |
Non-Affected Software
| Operating System |
|---|
| Microsoft Windows 2000 Service Pack 4 |
| Windows XP Service Pack 2 |
| Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2 |
| Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2 |
| Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition Service Pack 2 |
| Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems |
Frequently Asked Questions (FAQ) Related to This Security Update
I am using an older version 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 versions or editions are affected. Other versions or editions are past their support life cycle. To determine the support life cycle for your software version or edition, visit Microsoft Support Lifecycle.
It should be a priority for customers who have older versions or editions of the software to migrate to supported versions or editions 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 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 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.
Vulnerability Information
Severity Ratings and Vulnerability Identifiers
| Affected Software | SMBv2 Signing Vulnerability - CVE-2007-5351 | Aggregate Severity Rating |
|---|---|---|
| Windows Vista | **Important **\ \ Remote Code Execution | Important |
| Windows Vista x64 Edition | **Important **\ \ Remote Code Execution | Important |
SMBv2 Signing Vulnerability - CVE-2007-5351
A remote code execution vulnerability exists in the SMBv2 protocol that could allow a remote anonymous attacker to run code with the privileges of the logged-on user.
To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2007-5351.
Mitigating Factors for SMBv2 Signing Vulnerability - CVE-2007-5351
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:
- SMB signing is off by default in Windows Vista, which means that a computer running Microsoft Vista won’t use it unless it connects to another host which requires it.
- When a previous operating system version is part of the communications, SMBv2 will not be used. For example, Windows Vista would use SMB to communicate with Windows XP, rather than SMBv2.
- Customers using SMBv1 are not affected by this vulnerability.
Workarounds for SMBv2 Signing Vulnerability - CVE-2007-5351
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 SMBv2
To disable SMBv2, follow these steps:
Note: The following procedure is necessary only if the user wants to use SMB signing. If the user does not want to use SMB signing (the default condition except on a Windows Server 2008 domain), they do not need to do anything.
- Create a .reg file with the following contents:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation]
"DependOnService"=hex(7):42,00,6f,00,77,00,73,00,65,00,72,00,00,00,4d,00,52,
00,78,00,53,00,6d,00,62,00,31,00,30,00,00,00,4e,00,53,00,49,00,00,00,00,00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters]
"Smb2"=dword:00000000 - Run the .reg file by clicking it.
- Open a command prompt as Administrator.
- Run the following command:
sc config mrxsmb20 start= disabled - Restart the computer.
- Create a .reg file with the following contents:
Impact of workaround. Any performance improvements made to SMBv2 are not available if SMBv2 is disabled.
How to undo the workaround.
To enable SMBv2, follow these steps:
- Create a .reg file with the following contents:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation]
"DependOnService"=hex(7):42,00,6f,00,77,00,73,00,65,00,72,00,00,00,4d,00,52,
00,78,00,53,00,6d,00,62,00,31,00,30,00,00,00,4d,00,52,00,78,00,53,00,6d,00,62,
00,32,00,30,00,00,00,4e,00,53,00,49,00,00,00,00,00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters]
"Smb2"=dword:00000001 - Run the .reg file by double-clicking it.
- Open a command prompt as Administrator.
- Run the following command:
sc config mrxsmb20 start= demand - Restart the computer.
- Create a .reg file with the following contents:
FAQ for SMBv2 Signing Vulnerability - CVE-2007-5351
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
What causes the vulnerability?
SMBv2 signing is not correctly implemented in a way that could allow an attacker to modify an SMBv2 packet and re-compute the signature.
What is 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 and Windows Vista. SMBv2 can only be used if both client and server support it. 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 it can understand the new SMBv2 protocol. If the server (Windows Server 2008 or otherwise) understands SMBv2, then SMBv2 is chosen for subsequent communication. Otherwise the client and server use SMB 1.0.
What is SMBv2 Signing
SMBv2 signing is a feature through which all communications using the Server Message Block (SMB) protocol can be digitally signed at the packet level. Digitally signing the packets enables the recipient of the packets to confirm their point of origination and their authenticity.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. An attacker could then tamper with data transferred via SMBv2, which could allow remote code execution in domain configurations communicating with SMBv2. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
How could an attacker exploit the vulnerability?
An attacker could modify SMBv2 packets and impersonate a trusted source to perform malicious operations.
What systems are primarily at risk from the vulnerability?
Windows Vista systems that communicate using SMBv2 signing are primarily at risk.
What does the update do?
The update removes the vulnerability by correctly implementing signing for SMBv2 packets.
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.
Update Information
Detection and Deployment Tools and Guidance
Manage the software and security updates you need to deploy to the servers, desktop, and mobile computers in your organization. For more information see the TechNet Update Management Center. The Microsoft TechNet Security Web site provides additional information about security in Microsoft products.
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."
Finally, security updates can be downloaded from the Microsoft Update Catalog. The Microsoft Update Catalog provides a searchable catalog of content made available through Windows Update and Microsoft Update, including security updates, drivers and service packs. By searching using the security bulletin number (such as, “MS07-036”), you can add all of the applicable updates to your basket (including different languages for an update), and download to the folder of your choosing. For more information about the Microsoft Update Catalog, see the Microsoft Update Catalog FAQ.
Detection and Deployment Guidance
Microsoft has provided detection and deployment guidance for this month’s security updates. This guidance will also help IT professionals understand how they can use various tools to help deploy the security update, such as Windows Update, Microsoft Update, Office Update, the Microsoft Baseline Security Analyzer (MBSA), the Office Detection Tool, Microsoft Systems Management Server (SMS), and the Extended Security Update Inventory Tool. For more information, see Microsoft Knowledge Base Article 910723.
Microsoft Baseline Security Analyzer
Microsoft Baseline Security Analyzer (MBSA) allows administrators to scan local and remote systems for missing security updates as well as common security misconfigurations. For more information about MBSA, visit Microsoft Baseline Security Analyzer.
The following table provides the MBSA detection summary for this security update.
| Software | MBSA 2.0.1 |
|---|---|
| Microsoft Vista | See Note for Windows Vista below |
| Microsoft Vista x64 Edition | See Note for Windows Vista below |
Note for Windows Vista Microsoft does not support installing MBSA 2.0.1 on computers that run Windows Vista, but you may install MBSA 2.0.1 on a supported operating system and then scan the Windows Vista-based computer remotely. For additional information about MBSA support for Windows Vista, visit the MBSA Web site. See also Microsoft Knowledge Base Article 931943: Microsoft Baseline Security Analyzer (MBSA) support for Windows Vista.
For more information about MBSA 2.0.1, see MBSA 2.0 Frequently Asked Questions.
Windows Server Update Services
By using Windows Server Update Services (WSUS), administrators can deploy the latest Important updates and security updates for Windows 2000 operating systems and later, Office XP and later, Exchange Server 2003, and SQL Server 2000 to Windows 2000 and later operating systems. For more information about how to deploy this security update using Windows Server Update Services, visit the Windows Server Update Services Web site.
Systems Management Server
The following table provides the SMS detection and deployment summary for this security update.
| Product | SMS 2.0 | SMS 2003 |
|---|---|---|
| Microsoft Vista | No | See Note for Windows Vista below |
| Microsoft Vista x64 Edition | No | See Note for Windows Vista below |
For SMS 2.0, the SMS SUS Feature Pack, which includes the Security Update Inventory Tool (SUIT), can be used by SMS to detect security updates. See also Downloads for Systems Management Server 2.0.
For SMS 2003, the SMS 2003 Inventory Tool for Microsoft Updates (ITMU) can be used by SMS to detect security updates that are offered by Microsoft Update and that are supported by Windows Server Update Services. For more information about the SMS 2003 ITMU, see SMS 2003 Inventory Tool for Microsoft Updates. SMS 2003 can also use the Microsoft Office Inventory Tool to detect required updates for Microsoft Office applications. For more information about the Office Inventory Tool and other scanning tools, see SMS 2003 Software Update Scanning Tools. See also Downloads for Systems Management Server 2003.
Note for Windows Vista Microsoft Systems Management Server 2003 with Service Pack 3 includes support for Windows Vista manageability.
For more information about SMS, visit the SMS Web site.
For more detailed information, see Microsoft Knowledge Base Article 910723: Summary list of monthly detection and deployment guidance articles.
Security Update Information
Affected Software
For information about the specific security update for your affected software, click the appropriate link:
Windows Vista (all editions)
Reference Table
The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.
| Inclusion in Future Service Packs | The update for this issue will be included in a future service pack or update rollup |
|---|---|
| Deployment | |
| Installing without user intervention | Windows Vista:\ Windows6.0-kb942624-x86-enu /quiet |
| Windows Vista:\ Windows6.0-kb942624-x64-enu /quiet | |
| Installing without restarting | Windows Vista:\ Windows6.0-kb942624-x86-enu /norestart |
| Windows Vista:\ Windows6.0-kb942624-x64-enu /norestart | |
| Further information | See the subsection, Detection and Deployment Tools and Guidance |
| Restart Requirement | |
| Restart required | Yes, you must restart your system after you apply this security update |
| Hotpatching | This security update does not support HotPatching. For more information about HotPatching see Microsoft Knowledge Base Article 897341. |
| Removal Information | Windows Vista:\ WUSA.exe does not support uninstall of updates. To uninstall an update installed by WUSA, click Control Panel, and then click Security. Under Windows Update, click View installed updates and select from the list of updates. |
| File Information | See the next subsection, File Information, for the full file manifest. |
File Information
The English version of this security update has the file attributes that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
For all supported 32-bit editions of Windows Vista:
| File Name | Version | Date | Time | Size | Folder |
|---|---|---|---|---|---|
| mrxsmb20.sys | 6.0.6000.16586 | 26-Oct-2007 | 01:40 | 58,368 | Windows6.0-KB942624-x86\x86_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.0.6000.16586_none_88a4376b8cdaca70 |
| mrxsmb20.sys | 6.0.6000.20709 | 26-Oct-2007 | 01:55 | 58,368 | Windows6.0-KB942624-x86\x86_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.0.6000.20709_none_8987565aa5b4d3de |
| mrxsmb.sys | 6.0.6000.16586 | 26-Oct-2007 | 01:40 | 101,888 | Windows6.0-KB942624-x86\x86_microsoft-windows-smbminirdr_31bf3856ad364e35_6.0.6000.16586_none_7d5aaf055432589d |
| mrxsmb.sys | 6.0.6000.20709 | 26-Oct-2007 | 01:55 | 102,400 | Windows6.0-KB942624-x86\x86_microsoft-windows-smbminirdr_31bf3856ad364e35_6.0.6000.20709_none_7e3dcdf46d0c620b |
| srvnet.sys | 6.0.6000.16586 | 26-Oct-2007 | 01:40 | 84,992 | Windows6.0-KB942624-x86\x86_microsoft-windows-smbserver-common_31bf3856ad364e35_6.0.6000.16586_none_019f7004133c0031 |
| srvnet.sys | 6.0.6000.20709 | 26-Oct-2007 | 01:56 | 84,992 | Windows6.0-KB942624-x86\x86_microsoft-windows-smbserver-common_31bf3856ad364e35_6.0.6000.20709_none_02828ef32c16099f |
| srv2.sys | 6.0.6000.16586 | 26-Oct-2007 | 01:40 | 130,048 | Windows6.0-KB942624-x86\x86_microsoft-windows-smbserver-v2_31bf3856ad364e35_6.0.6000.16586_none_d7b5db3ef9909d40 |
| srv2.sys | 6.0.6000.20709 | 26-Oct-2007 | 01:56 | 130,560 | Windows6.0-KB942624-x86\x86_microsoft-windows-smbserver-v2_31bf3856ad364e35_6.0.6000.20709_none_d898fa2e126aa6ae |
For all supported x64-based editions of Windows Vista:
| File Name | Version | Date | Time | Size | CPU | Folder |
|---|---|---|---|---|---|---|
| mrxsmb20.sys | 6.0.6000.16586 | 26-Oct-2007 | 01:59 | 79,360 | x64 | Windows6.0-KB942624-x64\amd64_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.0.6000.16586_none_e4c2d2ef45383ba6 |
| mrxsmb20.sys | 6.0.6000.20709 | 26-Oct-2007 | 01:52 | 79,360 | x64 | Windows6.0-KB942624-x64\amd64_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.0.6000.20709_none_e5a5f1de5e124514 |
| mrxsmb.sys | 6.0.6000.16586 | 26-Oct-2007 | 02:00 | 133,632 | x64 | Windows6.0-KB942624-x64\amd64_microsoft-windows-smbminirdr_31bf3856ad364e35_6.0.6000.16586_none_d9794a890c8fc9d3 |
| mrxsmb.sys | 6.0.6000.20709 | 26-Oct-2007 | 01:52 | 134,144 | x64 | Windows6.0-KB942624-x64\amd64_microsoft-windows-smbminirdr_31bf3856ad364e35_6.0.6000.20709_none_da5c69782569d341 |
| srvnet.sys | 6.0.6000.16586 | 26-Oct-2007 | 02:01 | 118,272 | x64 | Windows6.0-KB942624-x64\amd64_microsoft-windows-smbserver-common_31bf3856ad364e35_6.0.6000.16586_none_5dbe0b87cb997167 |
| srvnet.sys | 6.0.6000.20709 | 26-Oct-2007 | 01:53 | 118,272 | x64 | Windows6.0-KB942624-x64\amd64_microsoft-windows-smbserver-common_31bf3856ad364e35_6.0.6000.20709_none_5ea12a76e4737ad5 |
| srv2.sys | 6.0.6000.16586 | 26-Oct-2007 | 02:01 | 162,304 | x64 | Windows6.0-KB942624-x64\amd64_microsoft-windows-smbserver-v2_31bf3856ad364e35_6.0.6000.16586_none_33d476c2b1ee0e76 |
| srv2.sys | 6.0.6000.20709 | 26-Oct-2007 | 01:53 | 164,352 | x64 | Windows6.0-KB942624-x64\amd64_microsoft-windows-smbserver-v2_31bf3856ad364e35_6.0.6000.20709_none_34b795b1cac817e4 |
Note For a complete list of supported versions, see the Support Lifecycle Index. For a complete list of service packs, see Lifecycle Supported Service Packs. For more information on the support lifecycle policy, see Microsoft Support Lifecycle.
Deployment Information
Installing the Update
When you install this security update, the installer checks to see if one or more of the files that are being updated on your system have previously been updated by a Microsoft hotfix.
For more information about the terminology that appears in this bulletin, such as hotfix, see Microsoft Knowledge Base Article 824684.
This security update supports the following setup switches.
| Switch | Description |
|---|---|
| /?, /h, /help | Displays help on supported switches. |
| /quiet | Suppresses the display of status or error messages. |
| /norestart | When combined with /quiet, the system will not be restarted after installation even if a restart is required to complete installation. |
Note For more information about the wusa.exe installer, see Microsoft Knowledge Base Article 934307.
Verifying that the Update Has Been Applied
Microsoft Baseline Security Analyzer
To verify that a security update has been applied to an affected system, you may be able to use the Microsoft Baseline Security Analyzer (MBSA) tool. See the section, Detection and Deployment Tools and Guidance, earlier in this bulletin for more information.
File Version Verification
Because there are several versions of Microsoft Windows, the following steps may be different on your computer. If they are, see your product documentation to complete these steps.
- Click Start, and then click Search.
- In the Search Results pane, click All files and folders under Search Companion.
- In the All or part of the file name box, type a file name from the appropriate file information table, and then click Search.
- In the list of files, right-click a file name from the appropriate file information table, and then click Properties.
Note Depending on the version of the operating system or programs installed, some of the files that are listed in the file information table may not be installed. - On the Version tab, determine the version of the file that is installed on your computer by comparing it to the version that is documented in the appropriate file information table.
Note Attributes other than the file version may change during installation. Comparing other file attributes to the information in the file information table is not a supported method of verifying that the update has been applied. Also, in certain cases, files may be renamed during installation. If the file or version information is not present, use one of the other available methods to verify update installation.
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.
- 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 (December 11, 2007): Bulletin published.
- V1.1 (December 19, 2007): Bulletin updated to reflect a change to the Removal Information text in the Reference Table portion of the Security Update Information section.
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