A security patch has been released that resolves a canonicalization error that can allow a malicious user to gain additional permissions to certain types of files that are hosted on a Web server.

For this vulnerability to be exploited, several factors are involved:

•	Only file types that are implemented through ISAPI extensions are affected. It does not affect static Web page or non-Web file types such as .exe, .doc, or .bat.
•	It only affects servers that expose a Web folder structure that mirrors the physical folder structure on the server. It does not impact virtual directories.
•	It does not allow arbitrary permissions to be selected, only permissions present on an ancestor folder.
•	It provides no ability to enumerate the server and locate files that can be affected by the vulnerability.

In addition to the above, this security patch also corrects the vulnerability described by the following article in the Microsoft Knowledge Base:

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Microsoft Exchange 2000 Server users and Microsoft SharePoint Portal Server 2001 users

Both Exchange 2000 and SharePoint Portal Server 2001 have problems with an older verison of this hotfix. A new update for the security patch for these products is available at the following Microsoft Web page:

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To resolve this problem, obtain the latest service pack for Windows 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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Internet Information Services 5.0

The following files are available for download from the Microsoft Download Center:
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. The English version of this fix should have the following file attributes or later:

   Date        Time    Version        Size     File name
   -----------------------------------------------------
   08-09-2000  1:02pm  5.0.2195.2103  357,136  W3svc.dll
				

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Internet Information Server 4.0

The following files are available for download from the Microsoft Download Center:

NOTE: Debug symbol files are required by an administrator to do both kernel and user mode debugging, providing a method to resolve global variables and function names in the loaded file. The symbol files are denoted with an "s" in the file name (for example, Prmcan4is.exe).

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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. The English version of this fix should have the following file attributes or later:

   Date        Time    Size     File name     Platform
   ---------------------------------------------------
   08/03/2000  05:06p  330,080  Asp.dll       Intel
   08/03/2000  05:04p  185,792  Infocomm.dll  Intel
   08/03/2000  05:05p   38,256  Ssinc.dll     Intel
   08/03/2000  05:05p   25,360  Sspifilt.dll  Intel
   08/03/2000  05:05p  228,496  W3svc.dll     Intel

   08/03/2000  05:08p  551,696  Asp.dll       Alpha
   08/03/2000  05:06p  304,912  Infocomm.dll  Alpha
   08/03/2000  05:07p   60,176  Ssinc.dll     Alpha
   08/03/2000  05:07p   39,696  Sspifilt.dll  Alpha
   08/03/2000  05:07p  384,272  W3svc.dll     Alpha
				

Microsoft Windows NT Server version 4.0, Terminal Server Edition

To resolve this problem, obtain the Windows NT Server 4.0, Terminal Server Edition, Security Rollup Package (SRP). For more information about the SRP, click the following article number to view the article in the Microsoft Knowledge Base:

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Microsoft has confirmed that this is a problem in Internet Information Services 5.0 and Internet Information Server 4.0.

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Additional information about this issue is available from the following Microsoft Web site: You can find frequently asked questions about this vulnerability at the following Microsoft Web site:

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