Can I use a wildcard certificate for a sub-subdomain?

Question

I have a domain, domain.tld. I installed a wildcard certificate for *.domain.tld, and I'd like to use it for super.sub.domain.tld. Is this possible?

Answer

Unfortunately, due to Domain Control Validation requirements, wildcard certificates cannot function on subdomains of subdomains relative to their issued root domain.

This would mean that a wildcard certificate for domain.tld, *.domain.tld, would be valid on bar.domain.tld, foo.domain.tld, x.domain.tld; but not foo.x.domain.tld, for example.

If you've purchased an external wildcard certificate and are unsatisfied with the coverage provided, we would advise either ensuring the certificate request includes all subdomains you'd like to utilize; or using our AutoSSL system, which will cover all domains registered in cPanel.

Resources

RFC 2818

How to convert to the cPanel-provided plugin for Let's Encrypt