This is described in CR# xos0063330;
Our development team has further investigated the problem and have found that this issue appears only in our older SSH Server, which is a SSH-toolkit implementation. From EXOS 16.2 and above releases, we are using OpenSSH for SSH server and this issue is not observed.
SSH-Toolkit Server supports only the below listed SSH-request types. Here "exec" is used for remote command execution, which works fine. But after the command is executed the client will request for a "exit-status" from the server. In SSH-Toolkit server, this message type is not supported. So, for "exit-status" request, Server replies with an error message. This is because it cannot process the request.
The valid channel requests in SSH-Toolkit and their actions are:
"pty-req" -- setup pty
"shell" -- start user shell
"exec" -- execute a command
"subsystem" -- handle subsystem calls (not implemented yet)
"env" -- determine if ENV variable is OK to be set, then set
"signal" -- if we have signals, send this signal to the process
"exit-status" -- send exit status to client, close connection (not supported - ignored)
"window-change" -- change terminal window size values
"xon-xoff" -- handle flow control (not supported - ignored)
"x11-req" -- channel request failure (not supported - ignored)
In EXOS 16.2 and 21.1 releases this issue would not exist as we have upgraded the SSH server to OPENSSH instead of SSH-Toolkit. However for EXOS releases lower than 16.2, this limitation would continue to exist.