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// DevOps, cloud & containers

Port 5303: HA cluster probing

Port 5303 is assigned by IANA to hacl-probe (HA cluster probing).

5303

How hacl-probe works

DevOps, cloud & containers
adminhosthacl-probe adminhosthacl-probe

Commands sent to port 5303 create and control containers or cluster resources on the host.

Transport
TCP · 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
DevOps, cloud & containers
01 Security

Is port 5303 dangerous?

We have no specific security note for port 5303. Its risk depends on the program actually listening on it. General advice for devops, cloud & containers services:

  • Container and orchestration APIs give full control of hosts: require mutual TLS and RBAC.
  • Never expose them to the Internet.
  • Rotate tokens and certificates and audit who has access.
02 Registry

IANA registry entries for port 5303

ServicePortTransportDescriptionReferenceUpdated
hacl-probe 5303 TCP, UDP HA cluster probing - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 5303, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5303'      # process listening on 5303
sudo lsof -nP -i :5303

macOS

sudo lsof -nP -i :5303

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5303 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5303
netstat -ano | findstr :5303

From another machine

nmap -p 5303 -sV <host>
sudo nmap -sU -p 5303 <host>
nc -zv <host> 5303

Block it in the firewall

sudo ufw deny 5303/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5303" -Direction Inbound -LocalPort 5303 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5303 used for?

Port 5303 is assigned by IANA to hacl-probe (HA cluster probing).

Is port 5303 TCP or UDP?

Port 5303 is registered for TCP and UDP.

Is it safe to open port 5303?

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. Container and orchestration APIs give full control of hosts: require mutual TLS and RBAC.

How do I check if port 5303 is open?

On Linux run "ss -ltnup 'sport = :5303'", on macOS "lsof -nP -i :5303", and on Windows "netstat -ano | findstr :5303" to see the local process. From another machine, "nmap -p 5303 <host>" shows whether it is reachable.

05 Related
:2375 Docker API (HTTP) tcp · critical risk :2376 Docker API (TLS) tcp · high risk :6443 Kubernetes API tcp · udp · high risk :10250 Kubelet API tcp · critical risk :2379 etcd tcp · critical risk :8500 Consul tcp · udp · high risk :4505 SaltStack tcp · critical risk :9000 PHP-FPM / SonarQube / Portainer tcp · udp · high risk

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