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// Databases & caches

Port 523: IBM-DB2

Port 523 is assigned by IANA to ibm-db2 (IBM-DB2).

523

How ibm-db2 works

Databases & caches
app:523ibm-db2 app:523ibm-db2

The application sends a SQL query to the ibm-db2 server on port 523, which returns rows from its tables.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
Databases & caches
01 Security

Is port 523 dangerous?

We have no specific security note for port 523. Its risk depends on the program actually listening on it. General advice for databases & caches services:

  • Bind the service to localhost or a private network, never to a public address.
  • Enable authentication, use per-application accounts and require TLS.
  • Watch for exposed Docker ports: publish them on 127.0.0.1 only.
02 Registry

IANA registry entries for port 523

ServicePortTransportDescriptionReferenceUpdated
ibm-db2 523 TCP, UDP IBM-DB2 - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 523, and is it reachable?

Linux

sudo ss -ltnup 'sport = :523'      # process listening on 523
sudo lsof -nP -i :523

macOS

sudo lsof -nP -i :523

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 523 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 523
netstat -ano | findstr :523

From another machine

nmap -p 523 -sV <host>
sudo nmap -sU -p 523 <host>
nc -zv <host> 523

Block it in the firewall

sudo ufw deny 523/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 523" -Direction Inbound -LocalPort 523 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 523 used for?

Port 523 is assigned by IANA to ibm-db2 (IBM-DB2).

Is port 523 TCP or UDP?

Port 523 is registered for TCP and UDP.

Is it safe to open port 523?

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. Bind the service to localhost or a private network, never to a public address.

How do I check if port 523 is open?

On Linux run "ss -ltnup 'sport = :523'", on macOS "lsof -nP -i :523", and on Windows "netstat -ano | findstr :523" to see the local process. From another machine, "nmap -p 523 <host>" shows whether it is reachable.

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