Hi,

I'm assumed this is for SharePoint 2013 and 2016 app. In this case, the CU is only needed to apply to K2 server(s). If you have client machines with K2 Studio or K2 for VS, then the CU will also need to apply to these machines. 

Hi,

Note, that If the K2 for SharePoint App has been added to a SharePoint site and a newer version of K2 is installed, it is necessary to update the app on each of the SharePoint sites.

Please go through the following documentation that provides a few steps on how to update K2 Sharepoint :

http://help.k2.com/kb001661

Kind Regards

Jaco