The 21th cumulative update release for SQL Server 2017 RTM is now available for download at the Microsoft Downloads site. Please note that registration is no longer required to download Cumulative updates.
To learn more about the release or servicing model, please visit:
CU21 KB Article: https://support.microsoft.com/en-us/help/4557397
Starting with SQL Server 2017, we are adopting a new modern servicing model. Please refer to our blog for more details on Modern Servicing Model for SQL Server
Microsoft® SQL Server® 2017 RTM Latest Cumulative Update: https://www.microsoft.com/download/details.aspx?id=56128 Update Center for Microsoft SQL Server: https://docs.microsoft.com/en-us/sql/database-engine/install-windows/latest-updates-for-microsoft-sql-server?view=sql-server-ver15