The issue
You are using ssh to login to a server with ssh key authentication and you get connection closed. On the server you are logging into the syslog shows as messages like
Oct 17 11:30:02 myserver sshd[27687]: [ID 800047 auth.crit] fatal: buffer_get: trying to get more bytes than in buffer
The fix
Check your authorized_keys file on the remote server. Use ssh-keygen -l -f ~/.ssh/authorized_keys
ssh-keygen -l -f ~/.ssh/authorized_keys
buffer_get: trying to get more bytes than in buffer
The above shows there is at least one key in your file that is the wrong format – usually because it is split over several lines rather than being just one long line. (note it could be any key in the file – not the one you are using from your server ) Once you fix the key then confirm with ssh-keygen that all is well – it should return a md5 checksum.
ssh-keygen -l -f authorized_keys
md5 1024 5d:35:7e:ad:3d:e6:70:6d:6f:1d:76:1a:46:ee:c1:c9 authorized_keys
Now retry your ssh access