- Patch VPN gateways quickly: they are a top initial access target.
- Use certificates or MFA rather than shared secrets.
- Investigate unexpected tunnels and proxies: they are also attacker tools.
Port 4755: GRE-in-UDP Encapsulation with DTLS
Port 4755 is assigned by IANA to gre-udp-dtls (GRE-in-UDP Encapsulation with DTLS).
4755
How gre-udp-dtls works
VPN, tunnels & proxiesTraffic is wrapped in a tunnel between the two ends, so the network in between only sees the tunnel.
- Transport
- UDP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
- VPN, tunnels & proxies
Is port 4755 dangerous?
We have no specific security note for port 4755. Its risk depends on the program actually listening on it. General advice for vpn, tunnels & proxies services:
IANA registry entries for port 4755
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| gre-udp-dtls | 4755 | UDP | GRE-in-UDP Encapsulation with DTLS | RFC 8086 | 2016-10-05 |
| - | 4755 | - | Reserved | - | - |
// source: IANA service name and port number registry
Which program uses port 4755, and is it reachable?
Linux
sudo ss -ltnup 'sport = :4755' # process listening on 4755
sudo lsof -nP -i :4755macOS
sudo lsof -nP -i :4755
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4755 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 4755 netstat -ano | findstr :4755
From another machine
nmap -p 4755 -sV <host> sudo nmap -sU -p 4755 <host> nc -zv <host> 4755
Block it in the firewall
sudo ufw deny 4755/udp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 4755" -Direction Inbound -LocalPort 4755 -Protocol UDP -Action Block # Windows
What is port 4755 used for?
Port 4755 is assigned by IANA to gre-udp-dtls (GRE-in-UDP Encapsulation with DTLS).
Is port 4755 TCP or UDP?
Port 4755 is registered for UDP.
Is it safe to open port 4755?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Patch VPN gateways quickly: they are a top initial access target.
How do I check if port 4755 is open?
On Linux run "ss -ltnup 'sport = :4755'", on macOS "lsof -nP -i :4755", and on Windows "netstat -ano | findstr :4755" to see the local process. From another machine, "nmap -p 4755 <host>" shows whether it is reachable.