Microsoft KB Archive/239931

= System Crashes When Unprivileged User Accesses Privileged IOCTL =

Article ID: 239931

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Enterprise Edition

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This article was previously published under Q239931



SYMPTOMS
When a user without the proper security privileges gains access to an Input/Output Control (IOCTL) with high security priveleges either by opening the device with trailing characters, using a relative open, or by obtaining the transport handle from the Windows Sockets Support driver (Afd.sys), the computer may stop responding (hang) and you may receive a STOP error message on a blue screen similar to the message listed below:

STOP 0X0000001E: KMODE_EXCEPTION_NOT_HANDLED



CAUSE
This behavior occurs because any access to an IOCTL needs to be available for users without the proper security privileges.



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



MORE INFORMATION
An IOCTL is a custom class of Input/Output Request Packets (IRP) available to User mode. Each Windows Driver Model (WDM) class driver has a set of IOCTLs that it uses to communicate with programs. The IOCTLs give the class driver information about intended usage by programs. The class driver performs all IOCTL parameter validation.

Additional query words: TCP/IP

Keywords: kbbug kbfix KB239931

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