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// Directory & authentication

Port 586: Password Change

Port 586 is assigned by IANA to password-chg (Password Change).

586

How password-chg works

Directory & authentication
userdirectorypassword-chgresponse userdirectorypassword-chgresponse

The client proves who it is on port 586 and gets an answer (or a ticket) it can use with other services.

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
Directory & authentication
01 Security

Is port 586 dangerous?

We have no specific security note for port 586. Its risk depends on the program actually listening on it. General advice for directory & authentication services:

  • Keep directory and authentication services on internal networks.
  • Require signing or TLS and disable anonymous queries.
  • Monitor authentication failures for spraying and brute force.
02 Registry

IANA registry entries for port 586

ServicePortTransportDescriptionReferenceUpdated
password-chg 586 TCP, UDP Password Change - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 586, and is it reachable?

Linux

sudo ss -ltnup 'sport = :586'      # process listening on 586
sudo lsof -nP -i :586

macOS

sudo lsof -nP -i :586

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 586 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 586
netstat -ano | findstr :586

From another machine

nmap -p 586 -sV <host>
sudo nmap -sU -p 586 <host>
nc -zv <host> 586

Block it in the firewall

sudo ufw deny 586/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 586" -Direction Inbound -LocalPort 586 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 586 used for?

Port 586 is assigned by IANA to password-chg (Password Change).

Is port 586 TCP or UDP?

Port 586 is registered for TCP and UDP.

Is it safe to open port 586?

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. Keep directory and authentication services on internal networks.

How do I check if port 586 is open?

On Linux run "ss -ltnup 'sport = :586'", on macOS "lsof -nP -i :586", and on Windows "netstat -ano | findstr :586" to see the local process. From another machine, "nmap -p 586 <host>" shows whether it is reachable.

05 Related
:389 LDAP tcp · udp · high risk :636 LDAPS tcp · udp · moderate risk :88 Kerberos tcp · udp · high risk :3268 Global Catalog (LDAP) tcp · udp · high risk :1812 RADIUS udp · tcp · moderate risk :31 MSG Authentication tcp · udp :49 Login Host Protocol (TACACS) tcp · udp :56 XNS Authentication tcp · udp

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