Out-of-Date MS SQL Server 2014 instance
Install the most recent service pack, then install the latest cumulative update.

According to SQL Server Builds, the most recent Service Pack for SQL Server 2014 is currently SP2.

CU10 is the most recent Cumulative Update.

Ensure you take a backup of your databases onto physically different media, and do this in a non-production environment to test the change prior to doing this to your production SQL Server.