Port 464 Kerberos passwd · TCP and UDP

What runs on port 464

Kerberos password change (kpasswd) and the Microsoft kadmin variant. A client that can get tickets on 88 but cannot change passwords is usually missing this port in a firewall rule.

Software that uses it: Active Directory · MIT Kerberos kadmind · FreeIPA

Should port 464 be open?

Private network or VPN only. Nothing good comes from this port being reachable from the internet. Keep it on an internal network, reach it over a VPN or an SSH tunnel, and firewall it from everything that does not need it.

• Needed on both TCP and UDP for Windows clients.

Check port 464

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :464'
ss -lunp 'sport = :464'
sudo lsof -i :464

# from another machine: is it reachable?
nc -zv host 464
nmap -p 464 host
nc -zuv host 464
sudo nmap -sU -p 464 host
curl -v telnet://host:464      # 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 464

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 464 proto tcp
sudo ufw allow from 10.0.0.0/8 to any port 464 proto udp
sudo ufw deny 464/tcp
sudo ufw deny 464/udp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 meta l4proto { tcp, udp } th dport 464 accept
nft add rule inet filter input meta l4proto { tcp, udp } th dport 464 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 464 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 464 -j DROP
iptables -A INPUT -p udp --dport 464 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p udp --dport 464 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=464 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 464" with no source is just "open".

Related ports

• 88 Kerberos — Authentication (Active Directory)
• 389 LDAP — Directory services; plaintext/STARTTLS
• 749 Kerberos admin — kadmin

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