Port 2083 cPanel (TLS) · TCP

What runs on port 2083

cPanel over TLS: the customer-facing control panel of a large share of shared web hosting. Also, unrelated, the IANA-registered port for RadSec (RADIUS over TLS). Being a login page for an entire hosting account, it needs 2FA and brute-force protection (cPHulk), which cPanel enables by default.

Software that uses it: cPanel · RadSec (FreeRADIUS, radsecproxy)

Should port 2083 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.

• WHM (the reseller/root side) is 2087; webmail is 2096.

Check port 2083

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :2083'
sudo lsof -i :2083

# from another machine: is it reachable?
nc -zv host 2083
nmap -p 2083 host
curl -v telnet://host:2083      # 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 2083

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 2083 proto tcp
sudo ufw deny 2083/tcp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 tcp dport 2083 accept
nft add rule inet filter input tcp dport 2083 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 2083 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 2083 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=2083 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 2083" with no source is just "open".

Putting it behind nginx

server {
    listen 443 ssl;
    server_name app.example.com;
    location / {
        proxy_pass http://127.0.0.1:2083;
        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 127.0.0.1:2083 only. Test which location block a request hits with the nginx location tester.

Related ports

• 2082 cPanel
• 2087 WHM (TLS) — cPanel root panel
• 1812 RADIUS auth

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