You can get stuck with your ssh session when your network is changing or when there’s a network disruption. You will face a lock leading to the unability to stop your session, even by doing a CTRL-C.
That’s why there’s some escape sequences you can use in that case (especially the first one when you’re stuck):
~. - terminate connection (and any multiplexed sessions)
~B - send a BREAK to the remote system
~C - open a command line
~R - Request rekey (SSH protocol 2 only)
~^Z - suspend ssh
~# - list forwarded connections
~& - background ssh (when waiting for connections to terminate)
~? - this message
~~ - send the escape character by typing it twice
Note that escapes are only recognized immediately after newline.