Intermediate certificate invalid through curl or openssl but valid in browser

 https://stackoverflow.com/questions/26218396/how-does-the-browser-deal-with-missing-intermediate-certs

Browsers will cache intermediate certificates. So if the missing certificate was already provided by another site the browser will have it already and will use it. But, if you use a fresh browser profile you might get the same problems as you get with curl, because the intermediate certificate is not cached.

This is at least how it works with Firefox. Other browsers might look into the Authority Information Access section of the certificate and if they find the URL issuer certificate they will download the certificate to continue with the chain verification.