An access violation may occur when you use an ISAPI filter in IIS 6.0

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SYMPTOMS

When you use an Internet Server API (ISAPI) filter that calls the GetServerVariable function to retrieve the AUTH_TYPE server variable before the user is authenticated, an access violation may occur.

Also, error messages that are similar to the following may be logged in the system event log:

Event Type: Warning
Event Source: W3SVC
Event Category: None
Event ID: 1009
Description: A process serving application pool 'DefaultAppPool' terminated unexpectedly. The process ID was '2928'. The process exit code was '0xc0000005'.

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CAUSE

The AUTH_TYPE server variable is populated from data that is contained in an internal object. The object stores information about the user and about how the user was authenticated. If the AUTH_TYPE server variable is requested in a filter before the user is authenticated in Microsoft Internet Information Services (IIS), the pointer to that internal object is NULL, and an access violation occurs.

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RESOLUTION

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support (http://support.microsoft.com/contactus/?ws=support)

Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

No prerequisites are required.

Restart requirement

You must restart your computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later 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.

    Date      Time     Version            Size    File name
   --------------------------------------------------------------
 25-Jan-2005  08:31  6.0.3790.256        9,728  W3comlog.dll     
 25-Jan-2005  08:31  6.0.3790.256      342,528  W3core.dll

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