IIS 6 applications may stop responding after you install Microsoft update KB 982666

In the last few days we have started seeing a new symptom appearing more and more often on IIS 6 servers. Here are the symptoms:

You are running Windows 2003 Server and you have IIS 6 installed and hosting your web-sites. The operating system prompts you to install Microsoft update MS10-040 (KB 982666). After completing the install you note the following errors:

  • IIS application pools or websites will no longer start
  • IIS web-sites may not be able to start.
  • Rapid Fail Protection will shut down your application pools 
  • An inspection of the event logs show that the IIS worker processes are terminating unexpectedly, showing event messages similar to the following:

Event Type: Warning
Event Source: W3SVC
Event Category: None
Event ID: 1009
Date:  12/9/2009
Time:  10:55:01 AM
User:  N/A
Computer: WEBSERVER01
A process serving application pool 'DefaultAppPool' terminated unexpectedly. The process id was '1234'.
The process exit code was '0xffffffff'.

Ensure that you are seeing the above process exit code '0xffffffff' for which this post applies.

So what really happens?

NOT ALL IIS installs running on Windows 2003 will be impacted by this patch. YOU CAN INSTALL the patch and continue running IIS normally. The only case when the error occurs is the following:

You installed Windows 2003 and you did not install IIS 6 when you did this. You then installed Service Pack 1 or Service Pack 2 directly and afterwards you decided to install IIS. When installing IIS you were prompted to insert the original installation disk (not the Service Pack 1 disk or the Service Pack 2 disk).

If you followed the scenario above, you will most likely end up with what is called a binary mismatch between the operating system dlls and the dlls that belong to IIS. In plain English: your Windows 2003 files are those of Service Pack 2 and your IIS files are those of Service Pack 1 or RTM.

How can you verify that you are in this scenario?

In a Windows 2003 command prompt, type the following command:


This will show you the Windows 2003 version that you are running and the patch level. You should see that the operating system is patched to Service Pack 2. If you are not, you should seriously consider upgrading since Service Pack 1 of Windows 2003 is no longer supported.

If you are running service pack 2, then go ahead and check the version of an IIS 6 files in the following folder: %windir%\system32\inetsrv. The minimum version of the file(s) is the following if you are running SP2.


What goes on behind the scenes?

The latest Microsoft update for Windows 2003 server updates the w3core.dll. This new version of the file will try and call an API located in iisutil.dll. The invoked API will only be found in the iisutil.dll that is installed by the Service Pack 2 of Windows 2003. If you installed IIS 6 after having installed Windows 2003 Service Pack 2, it is very possible, that the installer used the RTM or Service Pack 1 version of the dll, in which the API is not present. Thus the call fails.

Solution to this:

Should you find yourself in this situation, and only after you confirm the symptoms, you should go ahead and re-install the Service Pack 2 from Windows 2003. To download the Service Pack you can go to:


You do not need to un-install and re-install Service Pack 2, just re-install it. Upon install, the Service Pack installer will make a list of all Windows components that are installed on your system (including IIS) and will update their binaries.


This issue is specific to Windows Server 2003. We won’t run into this issue on a Windows 2008 server.

More update to follow on this issue soon…

*Reference/Credit for this post goes to this article for a similar issue earlier in December 2009 where KB973917 was causing similar issues.

Comments (11)

  1. Tom Stevens says:

    THANK you soooo much. Needed this fix!!!!

  2. Warren Walker says:

    Could you be more specific about affected DLLs and versions?  All of my IIS server's I've applied this patch to so far have some DLL's that are older than the recommended version  nntpsnap.dll and smtpsnap.dll are the most common that are always 6.0.3728.0 and iisclex4.dll is 6.0.3790.0 but nearly all the other DLL's are of the recommended version or higher.

    I also recommend your readers simply add the "File Version" column to explorer, instead of going to the properties of each individual file.

  3. john says:

    What about the Microsoft security patches and hotfixes applied?  Are we going to have to reinstalled all of those after the service reinstallation or WFP (windows file protection) will work for this ?

  4. Saur212 says:

    Warren, we have taken care of the concern around DLL. Please check the "What goes on behind the scenes?" section in the above post.

    John, no you don't have to reapply other patches/hotfixes after repplying SP2. SP2 does not replace the binaries that are at a higher version.

  5. Kevin says:

    Is this going to be fixed in the future ?

  6. Saur212 says:

    Yes, there will be more updates once we hear back on the from Product group.

  7. Isidro says:

    Hi, i Have this problem, but i can not fix. Make a update WIN2003 SP2 and then install IIS 6.0. we tray to install Windows Server  Update Service SP2 (WSUS). When i see the IIS 6.0  “DefaultAppPool” and “WsusPool” this STOP. When restart “DefaultAppPool” and “WsusPool” and when try to conect to Server with WSUS “WsusPool” it is Stops again. Now re-insntall SP2 in my Server2003, as topic says, and restart the server; the “DefaultAppPool” and “WsusPool” this STOP. Do you have another solución.

    If do you wants i can paste the Event Viewer.


  8. Isidro says:

    So? Any solution? Now install Virtual Server 2005 R2 and the same applies to the IIS, I check "Application Group" and the "DefaultAppPool" is stopped, reset the item and when I try to access the Virtual Server console from Internet Explorer I get SERVICE UNAVAILABLE , reviewed the "DefaultAppPool" and again this stopped.

    I talk to Microsoft support and they want my credit card to charge me the support that this is still an issue in conflict with SP2 update, and the other solution that I give is to ask in these forums.

    Please tell me if this forum is correct or that I follow him.


  9. Saur212 says:

    Hi, The KB article for this patch has been updated. Kindly have a look at support.microsoft.com/…/982666.

    If you are seeing the same exact issue, reapplying SP2 should resolve the issue. If reapplying Sp2 has not fixed the issue for you it could be possible that you are seeing a different issue. You can contact Microsoft support for help on this issue via proper process. IF the issue turns out to be related to this problem your credit card charge will be refunded anyway.

  10. david says:

    The same occurs to me.

    DefaultAppPool crashes.

    I can start it.

    Usign management console of citrix crashes again DefaultAppPool.

    I've Citrix CPS 4.5, Web Interface and CSG 3.

    I've Windows 2003 R2 SP2 Spanish version.

    w3core.dll is 6.0.3790.4693

    iisutil.dll is 6.0.3790.3959

    Dlls different to 6.0.3790.3959 are:

    w3dt.dll 6.0.3790.4693

    smtpsvc.dll   6.0.3790.4675

    seos.dll 6.0.3790.0

    infocomm.dll 6.0.3790.4215

    asp.dll 6.0.3790.4735

    aqadmin.dll 6.0.3790.0

    This is a critical server and need an urgent solution.

    Reapplying SP2 will fix it?

    Some comments say no.

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