Error message in Internet Explorer when you try to access a Web site that requires Kerberos authentication on a Windows XP-based computer: "HTTP Error 401 - Unauthorized: Access is denied due to invalid credentials"

You are using Microsoft Internet Explorer on a Microsoft Windows XP-based computer. When you try to access a Web site that requires Kerberos authentication, you may receive the following error message:

This problem may occur if the Web site uses a CNAME resource record in the Domain Name System (DNS) to contact the server that initiates Kerberos authentication. (This server also issues the Kerberos ticket.) When you use Internet Explorer to access the Web site, Internet Explorer uses the host name of the server instead of the CNAME resource record to contact the server. The authentication process does not work because only the Service Principal Name (SPN) for the CNAME resource record is registered on the account that is used for the authentication.

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.

Prerequisites

No prerequisites are required.

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.

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

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

After you apply software update 911149, follow these steps to enable this update:

1. Exit Internet Explorer.
2. Click Start, click Run, type regedit, and then click OK.
3. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
4. On the Edit menu, point to New, and then click Key.
5. Type FeatureControl, and then press ENTER.
6. With the
   FeatureControl
   registry subkey that you created in step 5 selected, point to New on the Edit menu, and then click Key.
7. Type FEATURE_USE_CNAME_FOR_SPN_KB911149, and then press ENTER.
8. With the
   FEATURE_USE_CNAME_FOR_SPN_KB911149
   registry subkey selected that you created in step 7, point to New on the Edit menu, and then click DWORD Value.
9. Type Iexplore.exe, and then press ENTER.
10. Right-click Iexplore.exe, and then click Modify.
11. In the Value data box, type 1, and then click OK.
    
    Note To revert to the previous behavior for backward compatibility, reset this value to 0x0.
12. Exit Registry Editor.

Note The feature control key FEATURE_USE_CNAME_FOR_SPN_KB911149 can also contain other applications, for example: If there are multiple applications, you can add a DWORD entry with the name of "*" and a value of 1 to activate this feature for all the installed applications that use URLs.

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base: