Microsoft KB Archive/911149

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

Article ID: 911149

Article Last Modified on 11/15/2007

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APPLIES TO


 * Microsoft Internet Explorer 6.0, when used with:
 * Microsoft Windows XP Professional

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Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry



SYMPTOMS
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:

HTTP Error 401 - Unauthorized: Access is denied due to invalid credentials.



CAUSE
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 now 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 service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or 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. To create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

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.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

After you apply software update 911149, follow these steps to enable this update:  Exit Internet Explorer. Click Start, click Run, type regedit, and then click OK. Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main

 On the Edit menu, point to New, and then click Key. Type FeatureControl, and then press ENTER.</li> With the  registry subkey that you created in step 5 selected, point to New on the Edit menu, and then click Key.</li> Type FEATURE_USE_CNAME_FOR_SPN_KB911149, and then press ENTER.</li> With the  registry subkey selected that you created in step 7, point to New on the Edit menu, and then click DWORD Value.</li> Type Iexplore.exe, and then press ENTER.</li> Right-click Iexplore.exe, and then click Modify.</li> 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.</li> Exit Registry Editor.</li></ol>

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

326985 How to troubleshoot Kerberos-related issues in IIS

824684 Description of the standard terminology that is used to describe Microsoft software updates

Keywords: kbhotfixserver kbwinxpsp2fix kbwinxpsp1fix kbbug kbfix kbqfe kbpubtypekc KB911149

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