CORS problems

I’m using Vaadin 14.1.4 and have problems setting Headers for CORS completely:

I have overridden CdiVaadinServlet#service
and call response.addHeader("Vary", "Origin");
before calling super.service(request, response).

If it got a request for
the response header is changed while calling super.serivice() by com.vaadin.flow.internal.ResponseWriter at line #158 by this statement: response.setHeader("Vary", "Accept-Encoding");

The problem: if my browser loads two HTML-pages from different servers that uses the same WebComponent (written with Vaadin 14) I get the error, that cache content belongs to a wrong origin.

What can I do to keep my setting of "Vary"?