Microsoft Security Bulletin MS08-063 – Important Vulnerability in SMB Could Allow Remote Code Execution (957095)

Microsoft Security Bulletin MS08-063 – Important
Vulnerability in SMB Could Allow Remote Code Execution (957095)
Published: October 14, 2008

Version: 1.0
General Information
Executive Summary

This security update resolves a privately reported vulnerability in Microsoft Server Message Block (SMB) Protocol. The vulnerability could allow remote code execution on a server that is sharing files or folders. An attacker who successfully exploited this vulnerability could install programs; view, change, or delete data; or create new accounts with full user rights.

This security update is rated Important for all supported editions of Microsoft Windows 2000, Windows XP, Windows Server 2003, 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 modifying the way that SMB handles file name length validation and file sharing. 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
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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

Important

MS06-063

Windows XP Service Pack 2

Remote Code Execution

Important

MS06-063

Windows XP Service Pack 3

Remote Code Execution

Important

None

Windows XP Professional x64 Edition

Remote Code Execution

Important

MS06-063

Windows XP Professional x64 Edition Service Pack 2

Remote Code Execution

Important

None

Windows Server 2003 Service Pack 1

Remote Code Execution

Important

MS06-063

Windows Server 2003 Service Pack 2

Remote Code Execution

Important

None

Windows Server 2003 x64 Edition

Remote Code Execution

Important

MS06-063

Windows Server 2003 x64 Edition Service Pack 2

Remote Code Execution

Important

None

Windows Server 2003 with SP1 for Itanium-based Systems

Remote Code Execution

Important

MS06-063

Windows Server 2003 with SP2 for Itanium-based Systems

Remote Code Execution

Important

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 957095.

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 SMB Buffer Underflow Vulnerability - CVE-2008-4038 Aggregate Severity Rating

Microsoft Windows 2000 Service Pack 4

Important
Remote Code Execution

Important

Windows XP Service Pack 2 and Windows XP Service Pack 3

Important
Remote Code Execution

Important

Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2

Important
Remote Code Execution

Important

Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2

Important
Remote Code Execution

Important

Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition Service Pack 2

Important
Remote Code Execution

Important

Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems

Important
Remote Code Execution

Important

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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SMB Buffer Underflow Vulnerability - CVE-2008-4038

A remote code execution vulnerability exists in the way that Microsoft Server Message Block (SMB) Protocol handles specially crafted file names. An attempt to exploit the vulnerability would require authentication because the vulnerable function is only reachable when the share type is a disk, and by default, all disk shares require authentication. An attacker who successfully exploited this vulnerability could 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-2008-4038.

Mitigating Factors for SMB Buffer Underflow Vulnerability - CVE-2008-4038

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 port should be blocked from the Internet.
•

Only authenticated users can trigger this vulnerability. This vulnerability can only be triggered if the user can authenticate against the remote system. However, if the Guest account is enabled, then guest users can trigger this vulnerability as well.
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Workarounds for SMB Buffer Underflow Vulnerability - CVE-2008-4038

Microsoft has not identified any workarounds for this vulnerability.
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FAQ for SMB Buffer Underflow Vulnerability - CVE-2008-4038

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 by insufficient validation of specially crafted file names by the Microsoft Server Message Block (SMB) Protocol.

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

How could an attacker exploit the vulnerability?
An attacker on a malicious client could exploit this vulnerability by sending specially crafted packets to a server. In order to exploit this vulnerability, an attacker must have the target host's IP address, NetBIOS computer name, and Port number in order to send the malicious traffic.

What systems are primarily at risk from the vulnerability?
Any Windows system that allows file sharing would be at risk.

What does the update do?
The update removes the vulnerability by adding SMB validation of particular file name lengths.

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:
•

Joshua Morin of Codenomicon for reporting the SMB Buffer Underflow Vulnerability (CVE-2008-4038)

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 (October 14, 2008): Bulletin published.