Error message when ISA Server 2004 Web Proxy client users try to access an external FTP site by using passive FTP functionality: "Error Code: 502 Proxy Error"

Consider the following scenario:

• You configure Microsoft Internet Security and Acceleration (ISA) Server 2004 to enable outgoing passive FTP traffic.
• You configure several internal client computers as ISA Server 2004 Web Proxy clients.

In this scenario, the internal Web Proxy clients can at first access external FTP sites and external Web sites. However, after several days or more, users receive the following error message when they use a Web Proxy client to access an external FTP site or an external Web site: Note You experience this problem only if the values for the registry subkey are set as follows on the computer that is running ISA Server 2004:

When ISA Server 2004 is configured in the manner that is described in the "Symptoms" section, ISA Server 2004 leaks socket endpoint handles. Specifically, ISA Server 2004 leaks a handle every time that a file is downloaded from an external FTP server.

Service pack information

To resolve this problem, obtain the latest service pack for Internet Security and Acceleration Server 2004. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Hotfix Information

ISA Server 2004, Standard Edition

Service pack information

To resolve this problem, obtain ISA Server 2004, Standard Edition Service Pack 2 (SP2). For more information, click the following article number to view the article in the Microsoft Knowledge Base:

ISA Server 2004, Enterprise Edition

Service pack information

To resolve this problem, obtain ISA Server 2004, Enterprise Edition Service Pack 2 (SP2). 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 be running ISA Server 2004 Enterprise Edition to install this hotfix. You cannot install this hotfix on a computer that is running ISA Server 2004 Standard Edition.

Restart requirement

You do not have to restart your computer after you apply this hotfix. However, ISA Server 2004-related services are automatically stopped and then restarted when you apply this hotfix.

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 tool in Control Panel.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk. To work around this problem, disable passive FTP functionality in ISA Server 2004. To do this, set the following values on the subkey:Note After you configure this registry entry, you must restart the ISA Server 2004 Firewall service for this change to take effect.

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 ISA Server 2004 Service Pack 2. This problem was first corrected in Internet Security and Acceleration Server 2004 Service Pack 2.

For more information about how to install ISA Server 2004 hotfixes and updates, click the following article number to view the article in the Microsoft Knowledge Base: For more information about the terms that are used in this article, click the following article number to view the article in the Microsoft Knowledge Base: