A buffer overflow (http://www.microsoft.com/technet/security/bulletin/glossary.mspx) that results in a privilege elevation (http://www.microsoft.com/technet/security/bulletin/glossary.mspx) vulnerability exists in Windows XP, Windows 2000, Windows NT 4.0, and Windows NT Server 4.0, Terminal Server Edition. If an attacker successfully exploits this vulnerability, the attacker gains complete control over the computer. This permits the attacker to take any action on the computer. These actions might include adding, deleting, or modifying data; creating or deleting user accounts; or adding accounts to the local Administrators group.

Mitigating factors:

•	The Multiple UNC Provider (MUP) request can be levied only by a process on the local computer. Therefore, this vulnerability can be exploited only by a user who can log on to an affected computer interactively (http://www.microsoft.com/technet/security/bulletin/glossary.mspx) and run code. By default, unprivileged users cannot interactively log on to Windows NT 4.0-based domain controllers. If typical security precautions have been taken, the only computers that are at risk are workstations and Terminal Services servers.
•	The buffer overflow does not always work in Windows 2000 because it depends on when the kernel manages the overflowed buffer. This is not externally controllable. Therefore, the computer will most likely display an error message on a blue screen or restart.
•	Best practices suggest that unprivileged users not be permitted to interactively log on to business-critical servers. If this recommendation has been followed, computers such as domain controllers, Enterprise Resource Planning (ERP) servers, print and file servers, database servers, and others are not be at risk from this vulnerability.

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This vulnerability occurs because the MUP service contains an unchecked buffer. By sending a specially malformed request, an attacker might be able to conduct a buffer-overrun attack against a computer.

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•	Windows XP
•	Windows XP 64-Bit Edition
•	Windows 2000
•	Windows NT 4.0
•	Windows NT Server 4.0, Terminal Server Edition

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Windows XP

To resolve this problem, obtain the latest service pack for Windows XP. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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Windows XP 64-Bit Edition

To resolve this problem, obtain the latest service pack for Windows XP. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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Windows 2000

To resolve this problem, obtain the latest service pack for Windows 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base: The following files are available for download from the Microsoft Download Center:
Release Date: April 4, 2002

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file. The English version of this fix should have the following file attributes or later:

   Date         Time   Version        Size    File name
   ----------------------------------------------------
   14-Mar-2002  18:07  5.0.2195.5080  87,024  Mup.sys
				

NOTE: Because of file dependencies, this update may contain additional files. This update requires Windows 2000 Service Pack 2 (SP2) (http://support.microsoft.com/kb/260910).

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Windows NT 4.0

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that you determine are at risk of attack. Evaluate the computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to the computer. See the associated Microsoft Security Bulletin (http://www.microsoft.com/technet/security/bulletin/ms02-017.mspx) to help determine the degree of risk. This hotfix may receive additional testing. If the computer is sufficiently at risk, we recommend that you apply this hotfix now.

To resolve this problem immediately, download the hotfix by following the instructions later in this article or contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site: Note In special cases, charges that are ordinarily incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The following file is available for download from the Microsoft Download Center:
Release Date: April 4, 2002

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file. Note that the information from Microsoft Knowledge Base article Q312895 was included in this article.

The English version of this fix should have the following file attributes or later:

   Date         Time   Version        Size    File name
   ----------------------------------------------------
   22-Jan-2002  20:43  4.0.1381.7125  80,752  Mup.sys
				

NOTE: Because of dependencies, this update may contain additional files. This update requires Windows NT 4.0 Service Pack 6a (SP6a) (http://support.microsoft.com/kb/152734).

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Windows NT Server 4.0, Terminal Server Edition

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that you determine are at risk of attack. Evaluate the computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to the computer. See the associated Microsoft Security Bulletin (http://www.microsoft.com/technet/security/bulletin/ms02-017.asp) to help determine the degree of risk. This hotfix may receive additional testing. If the computer is sufficiently at risk, we recommend that you apply this hotfix now.

To resolve this problem immediately, download the hotfix by following the instructions later in this article or contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site: Note In special cases, charges that are ordinarily incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The following file is available for download from the Microsoft Download Center:
Release Date: April 4, 2002

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file. Note that the information from Microsoft Knowledge Base article Q312895 was included in this article.

The English version of this fix should have the following file attributes or later:

   Date         Time   Version         Size    File name
   -----------------------------------------------------
   22-Jan-2002  20:50  4.0.1381.33522  82,224  Mup.sys
				

NOTE: Because of file dependencies, this update may contain additional files. This update requires Windows NT Server 4.0, Terminal Server Edition, Service Pack 6 (SP6) (http://support.microsoft.com/kb/152734).

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Windows XP and Windows XP 64-Bit Edition

Microsoft has confirmed that this problem may cause a degree of security vulnerability in Windows XP and Windows XP 64-bit Edition. This problem was first corrected in Windows XP Service Pack 1.

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Windows 2000

Microsoft has confirmed that this problem may cause a degree of security vulnerability in Windows 2000. This problem was first corrected in Windows 2000 Service Pack 3.

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Windows NT 4.0

Microsoft has confirmed that this problem may cause a degree of security vulnerability in Windows NT 4.0.

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Windows NT Server 4.0, Terminal Server Edition

Microsoft has confirmed that this problem may cause a degree of security vulnerability in Windows NT Server 4.0, Terminal Server Edition.

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For more information about this vulnerability, visit the following Microsoft Web site:

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