Microsoft KB Archive/248085

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

Article ID: 248085

Article Last Modified on 12/3/2007


  • Microsoft Internet Information Server 4.0
  • Microsoft Internet Information Services 5.0
  • Microsoft Internet Information Services 6.0

This article was previously published under Q248085

We strongly recommend that all users upgrade to Microsoft Internet Information Services (IIS) version 6.0 running on Microsoft Windows Server 2003. IIS 6.0 significantly increases Web infrastructure security. For more information about IIS security-related topics, visit the following Microsoft Web site:


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


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.


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

Additional query words: iis 4 iis4 iis 5 iis5 iis 6 iis 6.0 iis6

Keywords: kbprb kbpending kbprod2web KB248085