An access violation exception occurs in the "NdrClientCall2" function in Windows Vista or in Windows Server 2008

Consider the following scenario:

• You have a computer that is running Windows Vista or Windows Server 2008.
• You use some remote procedure calls (RPC) to send data between an RPC client and an RPC server.
• Some callback functions are called between the RPC client and the RPC server.

In this scenario, an access violation exception occurs in the NdrClientCall2�function on the RPC client. This access violation exception may cause data loss. Additionally, the memory usage of the RPC client keeps increasing.�

This issue occurs because the RPC driver (Rpcrt4.dll) handles an RPC call that involves the callback functions incorrectly.

When the call back function is called, the RPC client allows the RPC server to access some data of the RPC client. However, the RPC server does not notify the RPC client to free a buffer that may be used later when the callback function returns. This behavior causes a memory leak on the RPC client. Additionally, an access violation occurs when the RPC client tries to use the buffer again.��

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 the problem described in this article. 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, you must be running one of the following operating systems:

• Windows Vista Service Pack 1 (SP1)
• Windows Vista Service Pack 2 (SP2)
• Windows Server 2008
• Windows Server 2008 Service Pack 2 (SP2)

For more information about how to obtain a Windows Vista service pack, click the following article number to view the article in the Microsoft Knowledge Base: For more information about how to obtain a Windows Server 2008 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

Restart requirement

You may have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

File information

The global version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Important Windows Vista hotfixes and Windows Server 2008 hotfixes are included in the same packages. However, only "Windows Vista" is listed on the Hotfix Request page. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows Vista" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

• The files that apply to a specific product, SR_Level (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.

  Version	Product	SR_Level	Service branch
  6.0.600 1 . 22xxx	Windows Vista and Windows Server 2008	SP1	LDR
  6.0.600 2 . 22xxx	Windows Vista and Windows Server 2008	SP2	LDR

• Service Pack 1 is integrated into the release version of Windows Server 2008. Therefore, RTM milestone files apply only to Windows Vista. RTM milestone files have a 6.0.0000.xxxxx version number.
• 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. MUM files and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are 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

For all supported IA-64-based versions of Windows Server 2008

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

For more information about the NdrClientCall2 function, visit the following Microsoft Developer Network (MSDN) website: For more information about how to use RPC callback functions, click the following article number to view the article in the Microsoft Knowledge Base: For more information, click the following article number to view the article in the Microsoft Knowledge Base: For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

Additional file information

Additional file information for Windows Vista and for Windows Server 2008

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

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

Additional files for all supported IA-64-based versions of Windows Server 2008