Common attacks and weaknesses
- Stolen private keys give network access (no second factor in the protocol).
Port 51820: WireGuard
Default port of WireGuard VPN tunnels.
51820
How WireGuard works
VPN, tunnels & proxiesTraffic is wrapped in a tunnel between the two ends, so the network in between only sees the tunnel. Everything is encrypted: someone on the path only sees unreadable bytes.
- Transport
- UDP
- Exposure risk
- 2/10 low if reachable from the Internet
- Encryption
- EncryptedTLS or built-in crypto
- IANA status
- Unassignedcommon use differs from the registry
- Range
- Dynamic (49152-65535)
- Category
- VPN, tunnels & proxies
Is port 51820 dangerous?
How to secure it
- Protect and rotate keys; restrict AllowedIPs per peer.
Unofficial use. The IANA assignment below differs from what is usually found on this port in practice.
IANA registry entries for port 51820
No entry. The port is free for any application, so check what uses it on your hosts.
// source: IANA service name and port number registry
Which program uses port 51820, and is it reachable?
Linux
sudo ss -ltnup 'sport = :51820' # process listening on 51820
sudo lsof -nP -i :51820macOS
sudo lsof -nP -i :51820
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 51820 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 51820 netstat -ano | findstr :51820
From another machine
nmap -p 51820 -sV <host> sudo nmap -sU -p 51820 <host> nc -zv <host> 51820
Block it in the firewall
sudo ufw deny 51820/udp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 51820" -Direction Inbound -LocalPort 51820 -Protocol UDP -Action Block # Windows
What is port 51820 used for?
Default port of WireGuard VPN tunnels.
Is port 51820 TCP or UDP?
Port 51820 is registered for UDP.
Is it safe to open port 51820?
It is rated 2/10 (low) when exposed to the Internet. Stolen private keys give network access (no second factor in the protocol). Protect and rotate keys; restrict AllowedIPs per peer.
How do I check if port 51820 is open?
On Linux run "ss -ltnup 'sport = :51820'", on macOS "lsof -nP -i :51820", and on Windows "netstat -ano | findstr :51820" to see the local process. From another machine, "nmap -p 51820 <host>" shows whether it is reachable.