Custom domain + HTTPS gives NET::ERR_CERT_COMMON_NAME_INVALID only with apex domain

[alexanian]

Weird error for me. I have a custom domain hosted via Namecheap. I cofigured my A records the way recommended by the troubleshooting docs (see image below) and it _mostly _works.

In particular, all of the following links correctly redirect:

• https://www.catalystbiosummit.com
• http://www.catalystbiosummit.com (redirects to https://www.catalystbiosummit.com/)
• http://catalystbiosummit.com (redirects to https://www.catalystbiosummit.com/)

but:

• https://catalystbiosummit.com doesn’t work, and instead shows a privacy error, “NET::ERR_CERT_COMMON_NAME_INVALID”

The full message I get with the privacy error is:

“This server could not prove that it is  catalystbiosummit.com ; its security certificate is from www.github.com. This may be caused by a misconfiguration or an attacker intercepting your connection.”

What’s up? Is this a mixed content issue? Can I fix this with a redirect somehow?

Screenshot of DNS Config

[mkatwood]

Yo I have been dealing with a similar issue and this ended up solving my problem: https://medium.com/@monarchwadia/github-pages-setting-up-www-subdomain-with-ssl-https-aca9eca371d6

Maybe try this out and see if it does anything for you? Basically in the Github pages repo settings, I just had to make sure “www.” was in my custom domain and “enforce https” was checked. For some reason it wasn’t working when I just had the apex domain entered as the custom domain in settings.

Our problems are different since I was having the opposite problem, where the apex domain was working but it just wouldn’t work solely when using SSL *and* the www subdomain. Worth looking at though!

Hope you manage to fix your issue as well!

[hanneskl]

@alexanian Did you solve your issue?
@mkatwood Suggestion did not solve the issue for me.

[thomasshaped]

Hi @hanneskl, welcome to the GitHub Support Community! Pages only generates a cert for the exact domain you put in the custom domain in put. This answer should explain it a little further:

Apex Domain Issued Invalid Certificate with GitHub Pages Custom Domain

Hi @rajsite, GitHub Pages only generates an SSL certificate for the exact domain you enter in the custom domain input box. This means that only www.webvi.io will be secured. The apex domain webvi.io won’t be. This means that you’ll get a security error when you visit the HTTPS variant of your apex domain https://webvi.io/. You can still bypass this security error and you’ll be redirected to the secure version of your www subdomain, but the error will still show. This isn’t an issue if you visi…

[hanneskl]

Thanks, Thomas,
How can I run both apex and subdomain at the same time?
Use the apex and forward the subdomain to a webserver with a htaccess redirect to the apex?

[thomasshaped]

You can use both domains by setting up the correct DNS records for both of them but you aren’t able to secure both with an SSL cert.

You can follow the instructions here to set up your DNS, you’ll need to follow the steps to set up your apex domain and the www subdomain:

Managing a custom domain for your GitHub Pages site - GitHub Docs

Once you’ve set up both visiting www.example.com will automatically redirect to example.com (or vice-versa, depending on what version you put in you custom domain input). However, if you explicitly visit the HTTPS version of the domain not in your input box you’ll see an SSL error.