https://support.microsoft.com/en-gb/topic/kb4091266-on-demand-hotfix-update-package-for-sql-server-2012-sp4-21f2048f-a3a9-cd67-eaa3-01a3c51d02f3
KB4091266 - On-demand hotfix update package for SQL Server 2012 SP4 - Microsoft Support
Describes the on-demand hotfix update package for SQL Server 2012 SP4.