Nginx drop when server_name does not match

I have two vhosts : one on domain.tld port 80, the other on sub.domain.tld port 443 with SSL on. I added a CNAME entry on my DNS server that redirects my sub subdomain to domain.tld.. Everything works as expected, but going to http://sub.domain.tld does the same as going to http://domain.tld, and https://domain.tld the same as https://sub.domain.tld. How can I prevent this ?

My configuration :

server {
    listen *:443;
    listen [::]:443;

    server_name www.sub.domain.tld;

    ssl on;
    ssl_certifiate ...;
    ssl_certifiate_key ...;

    root /var/www/sub.domain.tld;
    ...
}

server {
    listen *:80;
    listen [::]:80;

    server_name www.domain.tld;

    root /var/www/domain.tld;
    ...
}