Sshd preauth child interrupted by signal 31

Question

The other day I upgraded to ubuntu 18.04, and since then I can not go back to my car. Auth.log tells me the following:

Jan 15 08:41:15 pc207 sshd[5358]: Accepted publickey for oscar from 10.60.0.15 port 42004 ssh2: RSA SHA256:59dtkmxMKMJG22+SQEoo7D55JSr+xlFjRyLMclLY210 Jan 15 08:41:15 pc207 sshd[5358]: debug1: monitor_child_preauth: oscar has been authenticated by privileged process Jan 15 08:41:16 pc207 sshd[5358]: debug1: monitor_read_log: child log fd closed Jan 15 08:41:16 pc207 sshd[5358]: fatal: privsep_preauth: preauth child terminated by signal 31 

So far, ssh -vvv localhost tells me the following:

 debug1: Authentication succeeded (publickey). Authenticated to localhost ([127.0.0.1]:22). debug1: channel 0: new [client-session] debug3: ssh_session2_open: channel_new: 0 debug2: channel 0: send open debug3: send packet: type 90 debug1: Requesting [e-mail] debug3: send packet: type 80 debug1: Entering interactive session. debug1: pledge: network debug3: send packet: type 1 packet_write_wait: Connection to 127.0.0.1 port 22: Broken pipe 

Google tells me to set UsePrivilegeSeparation to yes , no or sandbox , but it does nothing. My /etc/ssh/sshd not changed.

EDIT: I upgraded my personal laptop to 18.04 (HP Elitebook 8570w, completely unrelated to the above Dell), and the same error occurs when I try ssh on my laptop; preauth child interrupted by signal 31.

Answer 1

Perhaps a firewall, you can check:

 sudo ufw allow 22