When you open a device object in a program under the following conditions, it is possible to obtain greater access to that object than the designated permissions allow:

•	The device object has already been opened and you specify a relative file name of zero length to open a handle within that object.
•	The path specified to the device includes an additional trailing backslash name or character, and the device does not accommodate a parse routine.

This behavior particularly affects the following files in relation to I/O Manager:

•	Floppy.sys (Floppy Driver in C:\winnt\system32\drivers\)
•	Netdetect.sys (Network Card Detection driver Driver in C:\winnt\system32\drivers\)
•	Parport.sys (Parallel Port Driver in C:\winnt\system32\drivers\)
•	Null.sys (NULL Driver in C:\winnt\system32\drivers\)
•	Beep.sys (BEEP Driver in C:\winnt\system32\drivers\)
•	Scsiport.sys (SCSI Port Driver in C:\winnt\system32\drivers\)
•	Tcpip.sys (TCP/IP driver in C:\winnt\system32\drivers\)

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This problem occurs because it is the responsibility of a device driver of the corresponding device that creates or opens a logical DeviceObject in the operating system name space with IoCreateDevice() to represent the device. Detail of IoCreateDevice() can be found on MSDN at http://msdn.microsoft.com/library/ddkdoc/ntddk/native/ddk/kr/src/k104_22.htm (http://msdn2.microsoft.com/en-us/library/aa490468.aspx).

In Windows NT 4.0 Service Pack 6a and earlier, the seven aforementioned device drivers do not call IoCreateDevice() with the FILE_DEVICE_SECURE_OPEN DeviceCharacteristics. The seven that are included in the C2 Update (http://support.microsoft.com/kb/244599) call IoCreateDevice() with the FILE_DEVICE_SECURE_OPEN DeviceCharacteristics. The Windows NT IO manager that services IoCreateDevice() performs the necessary access check and audits the event if a relative file name of zero length is specified or an additional trailing backslash name or character is included in the path to the device.

NOTE: Other device drivers shipped with Windows NT 4.0 Service Pack 6a have been tested for making the IoCreateDevice() call with the FILE_DEVICE_SECURE_OPEN DeviceCharacteristics.

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To resolve this problem, the following files are available for download from the Microsoft Download Center or Microsoft's FTP site. Click the file names below to download the appropriate file:

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x86: FTP: Download Q244599i.exe now (ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/frn/nt40/hotfixes-postsp6a/c2-fix/Q244599i.exe)Alpha: FTP: Download Q244599a.exe now (ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/frn/nt40/hotfixes-postsp6a/c2-fix/Q244599a.exe)

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x86: FTP: Download Q244599i.exe now (ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/spa/nt40/hotfixes-postsp6a/c2-fix/Q244599i.exe)Alpha: FTP: Download Q244599a.exe now (ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/spa/nt40/hotfixes-postsp6a/c2-fix/Q244599a.exe) For additional 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 to prevent any unauthorized changes to the file.

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Microsoft has confirmed that this is a problem in Windows NT 4.0.

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