You are prompted for authentication four times when you try to access a file on a WebDAV server from a computer that is running Windows Vista or Windows Server 2008

Consider the following scenario:

• On a computer that is running Windows Vista or Windows Server 2008, you try to access a file on a Web Distributed Authoring and Versioning (WebDAV) server.
• This WebDAV server is located on an external network.
• You access the WebDAV server by using a proxy server that requires authentication.

Before you can open the file in this scenario, you are prompted for authentication four times. You expect to be prompted for authentication only two times.

Note You expect to be prompted to authenticate one time against the proxy server and the other time against the WebDAV server.

The behavior occurs because the WebDAV client does not correctly handle the "HTTP/1.1 407 Proxy Authentication Required ( Access is denied. ) /(HTTP_STATUS_PROXY_AUTH_REQ)" error. When this error is returned to the WebDAV client from the proxy server, the client maps this to the "ERROR_ACCESS_DENIED" error. Therefore, you are redundantly prompted for credentials.

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: 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

To apply this hotfix, the computer must run one of the following:

• Windows Vista Service Pack 1 (SP1)
• Windows Server 2008

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other previously released hotfixes.

Registry information

To use this hotfix, you do not have to make any changes to the registry.

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 item in Control Panel.

Windows Vista and Windows Server 2008 file information note

The MANIFEST files (.manifest) and MUM files (.mum) that are installed for each environment are listed separately . MUM and MANIFEST files, and the associated security catalog (.cat) files, are critical to maintaining the state of the updated component. The security catalog files (attributes not listed) are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows Server 2008 and of Windows Vista

For all supported x64-based versions of Windows Server 2008 and of Windows Vista

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

After you install this hotfix, the WebClient service sends the default logged-in credentials instead of the server credentials to pass through the proxy server. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Additional file information for Windows Server 2008 and for Windows Vista

Additional files for all supported x86-based versions of Windows Server 2008 and of Windows Vista

Additional files for all supported x64-based versions of Windows Server 2008 and of Windows Vista