Update: This issue has been resolved with new updates released by Microsoft.
Today, I had the pleasure of troubleshooting why a domain controller was continually, and randomly, rebooting itself. Though, rebooting is a light term, when the reality was the server was entering a fault state (aka, crashing) and rebooting to recover. Inspection of the event logs revealed Event ID 1074, which stated:
The process wininit.exe has initiated the restart of computer on behalf of user32 for the following reason: No title for this reason could be found
Reason Code: 0x50006
Shutdown Type: restart
Comment: The system process ‘C:\Windows\system32\lsass.exe’ terminated unexpectedly with status code [blank]. The system will now shut down and restart.
One or two Google searches later, refined to display only from the past week, I found a post where someone figured out that Microsoft Window’s Server 2012 R2 Security Update KB5009624 was the cause of the reboots, further detailed here.
Microsoft did release an emergency out of band update (KB5010794) though it is listed as an Optional update. So if you are not in the habit of installing those optional updates, now is a good time to start.
However, if you don’t want to install that optional update (for whatever reason), this fix is simple enough: either go to Windows Update -> Installed Updates -> and select it and click Uninstall; or, go to Control Panel -> Programs and Features -> View Installed Updates -> and select it and click Uninstall. (Note: a reboot will be required).