MS16-100: Description of the security update for Secure Boot: August 9, 2016

• All future security and non-security updates for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 require update 2919355 to be installed. We recommend that you install update 2919355 on your Windows RT 8.1-based, Windows 8.1-based, or Windows Server 2012 R2-based computer so that you receive future updates.
• If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.

Known issues in this security update

• When you try to install this security update, you may receive an error message that resembles the following:
   
  The update is not applicable to your computer
  
  Each Windows version requires a Servicing Stack Update (SSU). If you install updates by using Windows Update, Windows Server Update Services (WSUS), or the Microsoft Update Catalog, an SSU is automatically installed as part of the update. If you receive this error message, and if security update 3172729 is not already installed, you must install the corresponding SSU.

  OS Version	SSU KB #
  Windows Server 2016 TP5	3173423
  Windows Server 2012	3173426
  Windows 10 Version 1511	3173428
  Windows 10	3173427
  Windows 8.1 or Windows Server 2012 R2	3173424

• If you are running Windows 10 Version 1607 (Anniversary Edition), the Hyper-V firmware will already have the TP5 boot manager blacklisted.
  
  For example, when you set up Hyper-V on a Windows 10 Version 1607-based system, if you then create a Windows Server 2016 TP5-based virtual machine (VM), the VM does not start.
  
  To resolve this issue, follow these steps:
   
  1. Open the Hyper-V Manager, right-click the VM, and then select Settings.
  2. In the navigation pane, select Security.
  3. In the details pane, select Microsoft UEFI Certificate Authority in the Template list.
  4. In the details pane, click to clear the Enable Secure Boot check box, and then click OK.
     
     
      
  After you have installed TP5 on the VM and installed security update 3172729, re-enable secure boot. To do this, follow these steps:
  1. Open the Hyper-V Manager, right-click the VM, and then select Settings.
  2. In the navigation pane, select Security.
  3. In the details pane, click to select the Enable Secure Boot check box.
  4. In the details pane, select Microsoft Windows in the Template list, and then click OK.