Accessing session cookies across domains with CNAME

Question

Let's say there is domain A and domain B and domain A sets a session cookie on the domain .A.com. Now set a CNAME record that points subdomain.A.com to B.com. Will the browser that has visited subdomain.A.com have access to the cookie that was originally set by A.com, even though it is a CNAME that points to B.com?

Answer 1

No, CNAME is a DNS-level construct, and browsers do not take that into account at all. All it cares about is the host name in the URL.