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ssh error in syslog

Occasional Contributor

ssh error in syslog


I getting

sshd[18474]: channel_lookup: 0: bad id: channel free

sshd[18474]: Disconnecting: server_input_channel_req: unknown channel 0


  1. May I know it is ok to get  those message?
  2. I have try google around, but cant get any information what  does those message actually mean. Where can I get information on what  does the message mean?


Honored Contributor

Re: ssh error in syslog

1.) Maybe someone is connecting to your sshd and sending it bad data (or really anything that is not valid SSH protocol data).

It might be because someone has made a mistake and configured some application to connect to a wrong port.

It might be an enterprise monitoring system that is trying to see if your sshd is still running.

It might be a malicious person, sending bad data to try and make your sshd crash or let the malicious person log in without valid authentication.


2.) Only two ways:

- read OpenSSH source code (available at The HP SSH is a port of OpenSSH.

- ask OpenSSH developers or other people who really know the internal workings of OpenSSH.