ASP Incorrectly Decodes the QUERY_STRING and May Reveal the Metabase Path Information

You use the Response.QueryString collection to retrieve values from the end of an URL, but you do not receive the expected values. The values returned may instead be Internet Information Services (IIS) metabase information.

The Active Server Pages (ASP) intrinsic Request object contains information that is sent from the client to the server in an HTTP request. The QueryString collection contains any name/value pairs that appear at the end of the URL. For example: This information will be URL-encoded.


For example would appear as: However, if the value contains a percent sign and a hexadecimal value that does not map to a valid character ("%5F" maps to an underscore [_]), the return value of the collection will be the path of the Web site in the form of a metabase path. This can be a problem when the variable is printed directly into HTML through Response.Write.

For example would print out:

To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base: To resolve this problem, you can use the Server.URLEncode function to encode QueryString values before you add them to the QueryString.

For example:
If you print out the name value using on Page.asp, the result would be "My Name That Contains A % Sign" as expected.

Microsoft has confirmed that this is a problem in Microsoft Windows 2000.

This problem was first corrected in Windows 2000 Service Pack 1.