When visitors browse a Web site that is running Microsoft Internet Information Services (IIS) 6.0 with XML-based URL authorization stores, they may experience one or more of the following problems:

• Visitors experience slow performance.
• Visitors do not see images in Web pages. Visitors see picture placeholders that contain a red X instead of image files.
• Visitors receive the following error message in the browser:
  HTTP Error 500.18 - Server error: URL authorization store cannot be opened.

Note These problems are more likely to occur when the Web site experiences lots of visitors at the same time.

This problem occurs because the Urlauth.dll file incorrectly caches the XML authorization store. Therefore, the Urlauth.dll file must open the XML file every time that the Web site is accessed. When the Web site experiences lots of visitors at the same time, a sharing violation for the XML file may occur. When the sharing violation occurs, visitors experience the problems that are mentioned in the "Symptoms" section.

Service pack information

To resolve this problem, obtain the latest service pack for Windows Server 2003. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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

You must have Windows Server 2003 Service Pack 1 (SP1) installed to apply this hotfix.

Restart requirement

If the IIS service is running when you apply this hotfix, you must restart the IIS service.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

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.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Windows Server 2003 Service Pack 2.

For more information about the HTTP 500.18 internal server error code in IIS 6.0, visit the following Microsoft Web site: For more information about URL Authorization in IIS 6.0, visit the following Microsoft Web site: For more information about how to configure IIS 6.0 URL Authorization, click the following article number to view the article in the Microsoft Knowledge Base: