Digite os códigos de escape SSH! De man ssh
:
ESCAPE CHARACTERS
When a pseudo-terminal has been requested, ssh supports a number of
functions through the use of an escape character.
A single tilde character can be sent as ~~ or by following the tilde by a
character other than those described below. The escape character must
always follow a newline to be interpreted as special. The escape
character can be changed in configuration files using the EscapeChar
configuration directive or on the command line by the -e option.
The supported escapes (assuming the default ‘~’) are:
~. Disconnect.
~^Z Background ssh.
~& Background ssh at logout when waiting for forwarded connection /
X11 sessions to terminate.
Então: pressione Digite ~ . .