Port 8443 HTTPS alt · TCP

What runs on port 8443

The standard alternative HTTPS port: Tomcat with TLS, Plesk, UniFi's controller (8443), Kubernetes API on some distributions, VMware vCenter and many appliances' admin interfaces, plus Apache's and Nginx's usual choice when 443 is taken. It is HTTPS, so what matters is which product, whether it is patched, and whether its admin login should be reachable from where you are.

Software that uses it: Apache Tomcat (TLS) · Plesk · UniFi Network application · Kubernetes (some distros) · VMware, Fortinet, appliances

Should port 8443 be open?

Internet-facing only with authentication and care. It can be exposed when the service behind it is authenticated, rate-limited and kept up to date; most deployments are better off behind a VPN, an allow-list or a reverse proxy.

• openssl s_client -connect host:8443 | openssl x509 -noout -subject -issuer usually names the product in the certificate.
• Appliance admin interfaces on 8443 have a bad vulnerability record; keep them on a management network.

Check port 8443

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :8443'
sudo lsof -i :8443

# from another machine: is it reachable?
nc -zv host 8443
nmap -p 8443 host
curl -v telnet://host:8443      # raw TCP connect test, Ctrl-C to leave

A port that answers from the internet when it should not is the finding; nmap from a machine outside your network (or a VPS) is the honest test, because scans from inside the LAN pass the firewall you are trying to verify.

Allow or block port 8443

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 8443 proto tcp
sudo ufw deny 8443/tcp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 tcp dport 8443 accept
nft add rule inet filter input tcp dport 8443 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 8443 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8443 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=8443 protocol=tcp accept'

Replace 10.0.0.0/8 with the networks that need access. Allowing by source address is the rule that matters; "allow 8443" with no source is just "open".

Putting it behind nginx

server {
    listen 443 ssl;
    server_name app.example.com;
    location / {
        proxy_pass http://127.0.0.1:8443;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto https;
    }
}

Then make the application listen on 127.0.0.1:8443 only. Test which location block a request hits with the nginx location tester.

Related ports

• 443 HTTPS — Web over TLS; UDP for HTTP/3 (QUIC)
• 8080 HTTP alt — Tomcat, proxies, dev servers
• 4443 HTTPS alt
• 10443 HTTPS alt

Part of the port number reference. Ports are 16-bit numbers; see also the subnet calculator and the packet decoder, which shows ports inside TCP and UDP headers.

Questions