Port 27017 — MongoDB

TCP registered

What runs on port 27017

The default MongoDB port.

MongoDB. Versions before 3.6 bound to all interfaces by default with no authentication, which produced a long series of mass-ransom incidents where databases were wiped and a bitcoin address left in their place. The default is now localhost, but the pattern still appears in containers and cloud images that override it for convenience.

Security considerations

Older versions bound to all interfaces with no authentication, which led to mass ransoming of exposed databases. Enable auth and bind privately.

Checking whether something is listening

# Linux / macOS — what is bound to the port
sudo lsof -i :27017
sudo ss -lntp | grep :27017

# Windows
netstat -ano | findstr :27017
Get-NetTCPConnection -LocalPort 27017

# is it reachable from outside?
nc -zv example.com 27017
curl -v telnet://example.com:27017

Freeing the port

# find the process, then stop it
sudo lsof -ti :27017 | xargs kill        # Linux / macOS
netstat -ano | findstr :27017            # note the PID, then:
taskkill /PID <pid> /F                    # Windows

Should this port be open to the internet?

No. Port 27017 should never be reachable from a public address. Bind it to localhost or a private network, and reach it through a VPN or bastion host if remote access is genuinely needed. Internet-wide scanners find newly exposed instances of this service within minutes.

Opening or blocking port 27017

There is no blanket-allow rule on this page, because there is no case for one. MongoDB on port 27017 should be reachable from named addresses or not at all, so what follows restricts rather than opens:

# ufw — Debian, Ubuntu
sudo ufw allow from 10.0.0.0/8 to any port 27017 proto tcp
sudo ufw deny 27017/tcp                    # everything else

# firewalld — RHEL, Fedora, CentOS
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=27017 protocol=tcp accept'
sudo firewall-cmd --reload

# iptables, if you are still there
sudo iptables -A INPUT -p tcp --dport 27017 -s 10.0.0.0/8 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 27017 -j DROP

# Windows
New-NetFirewallRule -DisplayName "MongoDB 27017" -Direction Inbound -Protocol TCP -LocalPort 27017 -RemoteAddress 10.0.0.0/8 -Action Allow

Change 10.0.0.0/8 to whatever your private range actually is. A firewall rule is the second line: the first is binding the service to a private interface, because a service that only listens on 127.0.0.1 cannot be reached however the firewall is configured.

Quick reference

Frequently asked questions

Other common ports

• Port 20 — FTP data
• Port 21 — FTP control
• Port 22 — SSH / SFTP
• Port 23 — Telnet
• Port 25 — SMTP
• Port 53 — DNS
• Port 67 — DHCP server
• Port 68 — DHCP client
• Port 69 — TFTP
• Port 80 — HTTP
• Port 110 — POP3
• Port 123 — NTP
• Port 143 — IMAP
• Port 161 — SNMP
• Port 389 — LDAP
• Port 443 — HTTPS
• Port 445 — SMB
• Port 465 — SMTPS

All port numbers