Article ID: 248085 - Last Review: July 7, 2008 - Revision: 5.1

Error Message: HTTP 401.5 - Unauthorized: Authorization by ISAPI or CGI Application Failed

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We strongly recommend that all users upgrade to Microsoft Internet Information Services (IIS) version 7.0 running on Microsoft Windows Server 2008. IIS 7.0 significantly increases Web infrastructure security. For more information about IIS security-related topics, visit the following Microsoft Web site:

http://www.microsoft.com/technet/security/prodtech/IIS.mspx (http://www.microsoft.com/technet/security/prodtech/IIS.mspx)

For more information about IIS 7.0, visit the following Microsoft Web site:

http://www.iis.net/default.aspx?tabid=1 (http://www.iis.net/default.aspx?tabid=1)

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SYMPTOMS

When you attempt to access an IIS Web site, the following error message may occur:

HTTP 401.5 - Unauthorized: Authorization by ISAPI or CGI application failed

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CAUSE

The Web address has an ISAPI (Internet Server Application Programming Interface) or CGI (Common Gateway Interface) program that verifies user credentials. The authentication credentials used to connect to the server were denied access by this program.

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RESOLUTION

To resolve this issue, attempt to access the server again using the appropriate credentials. Contact the system administrator to obtain the correct logon information.

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