Windows Remote Management (WinRM) does not accept HTTP authorization requests that are larger than 16 KB on a computer that is running Windows Server 2008 or Windows Vista

Consider the following scenario:

• You have Windows Remote Management (WinRM) installed on a computer that is running Windows Server 2008 or Windows Vista.
• You have a user security token that is larger than 16 KB because of the domain configuration.
  
  Note The size of the user security token grows together with the number of groups to which the user belongs.
• You start a WinRM operation from this computer. Or, you use another application that uses WinRM for communication, such as Microsoft System Center Virtual Machine Manager.

In this scenario, the operation fails and you receive following error code: Additionally, the following event is logged in the System log:

Log Name: System
Source: Microsoft-Windows-Security-Kerberos
Date: Date & Time
Event ID: 6
Task Category: None
Level: Warning
Keywords: Classic
User: N/A
Computer: Computer Name
Description: The kerberos SSPI package generated an output token of size number bytes, which was too large to fit in the token buffer of size number bytes, provided by process id number. The output SSPI token being too large is probably the result of the user user name being a member of a large number of groups. It is recommended to minimize the number of groups a user belongs to. If the problem can not be corrected by reduction of the group memberships of this user, please contact your system administrator to increase the maximum token size, which in term is configured machine-wide via the following registry value: HKLM\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters\MaxTokenSize.

If you run command "winrm identify -remote: <name-of-remote-machine>" at the command prompt, you will receive the follwoing error message:

In some domain environments, the user security token that is used to authenticate the user to the server may be larger than 16 KB. This can occur when a user is a member of many security groups.

However, WinRM has a 16 KB size limit for HTTP authorization requests. Therefore, WinRM does not accept HTTP authorization requests that use a user security token that is larger than 16 KB.

A hotfix is available to resolve this issue. After you apply this hotfix, you can customize the values of MaxFieldLength and MaxRequestBytes registry entries to make WinRM accept authorization requests larger than 16 KB.

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, your computer must be running one of the following operating systems:

• Windows Vista Service Pack 1
• Windows Vista Service Pack 2
• Windows Server 2008
• Windows Server 2008 Service Pack 2

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

After you apply this hotfix, you can customize the following two registry entries to make WinRM accept authorization requests larger than 16KB.

The MaxFieldLength registry entry

The MaxRequestBytes registry entry

Typically, the MaxFieldLength registry entry is configured together with the MaxRequestBytes registry entry. If the MaxRequestBytes value is less than the MaxFieldLength value, the MaxFieldLength value is adjusted.

For more information about the Http.sys registry settings, click the following article number to view the article in the Microsoft Knowledge Base:

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 the 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 Vista and of Windows Server 2008

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

For all supported Itanium-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, 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:

Additional file information for Windows Vista and for Windows Server 2008

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

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

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