The PrincipalContext.ValidateCredentials method returns a false value even when you use valid credentials on a Windows Server 2008 SP2-based server that has AD LDS installed

You install Active Directory Lightweight Directory Services (AD LDS) on a server that is running Windows Server 2008 Service Pack 2 (SP2). When AD LDS is under a heavy load, the PrincipalContext.ValidateCredentials method in the System.DirectoryServices.AccountManagment namespace returns a false value even when you use valid credentials.

Because of this problem, you experience one or more of the following issues.

Issue 1

When a user logs on by using valid credentials, the server reports an invalid credentials failure and then requires the user to enter other credentials.

Issue 2

Some operations that require post logon to access the directory service fail. When you check the network trace, you find an �invalid credentials� error.

This problem occurs because the directory service has no bandwidth to validate credentials. Therefore, the directory service returns an LDAP_INVALID_CREDENTIALS error code to the PrincipalContext.ValidateCredentials method.

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 Windows Server 2008 SP2 on the computer. 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 must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English (United States) 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.

Windows Server 2008 file information notes

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 (SP2), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.
  Collapse this tableExpand this table

  Version	Product	SR_Level	Service branch
  6.0.600 2 . 22xxx	Windows Server 2008	SP2	LDR

• 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 SP2 section. MUM files and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to 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 x86-based versions of Windows Server 2008 SP2

For all supported x64-based versions of Windows Server 2008 SP2

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

After you install this hotfix, AD LDS returns an LDAP_OTHER error to the PrincipalContext.ValidateCredentials method when AD LDS has no bandwidth to validate credentials. Then, the PrincipalContext.ValidateCredentials method throws a Lightweight Directory Access Protocol (LDAP) exception instead of returning a true value or a false value.

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