I searched for many questions in the forum about setting cookies across domains and subdomains but I don't find this exact scenario. I've created a cookie in my subdomain sub1.example.com and my configuration is something like:

var cookieDomain = ".example.com";

When I visit any other subdomain it works fine and the cookie is set all around. The problem is in the main website www.example.com, it doesn't work at all and can't read the cookie.

How can I set a cookie in a subdomain and use it in main domain?