Applications or services that call the WNetOpenEnum function may crash when the number of network providers exceeds 16 on a Windows Server 2008-based computer

Consider the following scenario:

• You have more than 16 network providers on a Windows Server 2008-based computer.
• An application calls the WNetOpenEnum function to enumerate the network resources.

In this scenario, the application may encounter an access violation and then crash.

This problem may occur because the Multiple Provider Router (MPR) module does not manage allocated memory space correctly when the number of network providers exceeds 16.

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.

Important Windows Vista and Windows Server 2008 hotfixes are included in the same packages. However, only one of these products may be listed on the �Hotfix Request� page. To request the hotfix package that applies to both Windows Vista and Windows Server 2008, just select the product that is listed on the page.

Prerequisites

To apply this hotfix, you must have Windows Server 2008 and Windows Vista Service Pack 1 (SP1) installed.

Note Windows Vista SP1 is integrated into 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 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.

Note The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008 and for Windows Vista" section. MANIFEST and MUM files and the associated security catalog (.cat) files are very important for maintaining the state of the updated component. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For all supported 32-bit versions of Windows Server 2008 and of Windows Vista

For all supported 64-bit versions of Windows Server 2008 and of Windows Vista

For all supported Windows Server 2008 Itanium-Based Systems operating systems

Additional file information for Windows Server 2008 and of Windows Vista

Additional files for all supported 32-bit versions of Windows Server 2008 and of Windows Vista

Additional files for all supported 64-bit versions of Windows Server 2008 and of Windows Vista

Additional files for all supported Windows Server 2008 Itanium-Based Systems operating systems

To work around this problem, uninstall any network providers that you do not regularly use.

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

A network provider is a .dll file that enables Windows to interact with other kinds of networks, such as with Novell networks. A network provider is a client of the Windows WNet driver. A network provider implements network-specific actions, such as creating a connection. Additionally, it exposes a common interface to Windows. This interface is called the Network Provider API, and it consists of functions that are implemented by the network provider. You can create a network provider DLL to support new network protocols.

Because each network exposes a common interface through its provider, Windows can interact with several kinds of networks without knowing their network-specific implementation details.

The Multiple Provider Router (MPR) handles communication with all the network providers on the system, and it presents an integrated network to the user.

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: