To check if the proxy is listening on port 443 there are 2 ways:
Look for "port 443".
look for a service listening on port 443.
Then there is the very unusual possibility that someone in Management Services has changed the GUI from 8082 to 443.
From a security point of view, this is unattractive and even dangerous, because it makes it easier for hackers to do their work, since 443 is frequently enabled on the firewall.
Once you have found a service, the next step is to make sure that you find this service in the rule set.
Then the proxy should have a forwarding to a server in the forward layer - and this server will probably have the reported vulnerability.
If it is a forward proxy, then there is still the possibility that the scanner surfed through the proxy to a website that has this vulnerability.