Currently we get SESSION_HAS_VALID_POOL_ON_EXIT (ab) BSODs regularly on our Windows Server 2012 servers. These servers are used as XenApp servers and therefore a BSOD on such a server is pain in the ass when you have 50 users or even more working on such a server.

Finally Microsoft confirmed that this is a bug and they are now working on a fix. I will update this post as soon as I get a hotfix that resolves the issue.

The windbg output looks as follow:



Update 05.09.14: I got a private hotfix from Microsoft that definitively fixes the issue. I informed the Microsoft engineer today that they can start to initiate the process to release a public hotfix. We have seen the BSOD 1-2 times per day, and it completely disappeared since we applied the hotfix. There seems to be another bug we discovered by another BSOD that Microsoft is analyzing, but finally no AB BSOD!

Update 11.02.15: The fix has now been released for public:
More Information:


  1. Hi we have a 2012R2 server in running RDS which is having the same problem as of today. It happens when any user/admin logs off from their session.

    • Hi Sam – is it just frequently? We are currently testing a private hotfix from Microsoft. I will be able to tell you in 2 weeks if it fixed the issue. But I believe our private hotfix only works for Server 2012 (and not R2). I suggest that you open a support case with Microsoft because finding the root cause of the issue is very difficult in win32k.sys, even for Microsoft.

      – Regards, Michael

  2. Hi

    We had the same issue because of the faulty hotfix KB2982791. After deinstalling it, everything was fine. But then this happened again with the “corrected” hotfix KB299365. After the deinstallation of this hotfix too, the users can logoff again without producing a bluescreen.


    • Hi Nicola,

      Thanks for your message! It’s interesting that you won’t get the BSOD without these hotfixes. We got it as well without these fixes, but just occasionally. Means that the new hotfixes even enforce the BSODs more often. I just updated my post, I got a private hotfix and it fixed the issue in our environment. I assume there will soon be a public update for that issue…stay tuned!

      – Regards, Michael

      • Hi Michael, I have the same issues even with the KB299365.
        Ran the dedugger also and got exactly the same results. Would you mind sharing the hotfix? or at least a case number to so we could speed up the process?

        Best Regards,

        • Hi Sander,

          Sure, this is the Microsoft case number: 114042911399101. Note that there is still no public hotfix, we still use the private hotfix that is unsigned. Microsoft is currently working on a public hotfix. But I think that will take some time….

          Regards, Michael

  3. Thank you for you reply, I’m currently investigating, but it seems that disabling legacy graphics mode en enabling desktop composition redirection seemed reduce the frequency of errors. (to short to say it solves ) We however need legacy for some applications…

  4. We also use legacy graphics mode, that’s probably whey we saw the issue happening more often. The bug is related to graphics, surface cleanup support has been enhanced from what I understood. Anyway, the issue disappeared since we applied the fix, so do that and it’s gone…

    • The hotfix is going to be released for public in January 2015. But that hotfix won’t work with your Windows 2008 R2 server, it’s a fix for Windows Server 2012.
      – Regards, Michael

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