Users in a trusted external Kerberos realm cannot access resources from a Windows Server 2003-based forest to another forest by using a forest trust and a Kerberos trust

Consider the following situation:

• You have two Microsoft Windows Server 2003-based forests, ForestA and ForestB.
• You have an external Kerberos realm.
• A forest trust is created between ForestA and ForestB.
• A Kerberos trust is created between ForestA and the Kerberos realm.
• A user account in the Kerberos realm is mapped to a user account in ForestA.
• A user logs on to a computer in ForestB by using the mapped user account.

In this scenario, if the user tries to access the resources that are in ForestA, the user is repeatedly prompted for user credentials in order to access the resources that are in ForestA. Eventually, the user cannot access the resources because the logon fails.

Additionally, the following event is logged on the client computer:

Event Type: Warning
Event Source: LSASRV
Event Category: SPNEGO (Negotiator)
Event ID: 40960
User: <UserName>
Computer: <ComputerName>
Description:
The Security System detected an attempted downgrade attack for server <Server FQDN>. The failure code from authentication protocol Kerberos was "The name or SID of the domain specified is inconsistent with the trust information for that domain. (0xc000019b)".

To resolve this problem, apply the appropriate version of the hotfix on all computers that are running Microsoft Windows XP or Windows Server 2003.

Hotfix information

Windows XP

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

To apply this hotfix, you must have Windows XP Service Pack 2 (SP2) installed on the computer. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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.

Windows XP

Windows Server 2003

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

To apply this hotfix, you must have Windows Server 2003 Service Pack 1 (SP1) or Windows Server 2003 Service Pack 2 (SP2) installed on the computer. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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.

Windows Server 2003, x86-based versionsWindows Server 2003, Itanium-based versionsWindows Server 2003, x64-based versions

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: