Weird behaviour of OpenSSH server eating slowly all the available memory

I have a machine running a pgbouncer server and an Open SSH server so clients can enstabilish a tunnel to the server and connect to the database. Now all the clients keep the connection alive for around 3 minutes, then the connection is closed. As you can see the following image shows you that running the command: ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc multiple times underline the fact that the number or sshd processes decreases over a shor period of time. sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 158 158 790 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 150 150 750 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 146 146 730 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 140 140 700 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 140 140 700 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 140 140 700 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 140 140 700 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 136 136 680 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 132 132 660 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 132 132 660 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 132 132 660 sosepe@pgbouncer:~$ netstat -nt | grep :22 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 298 298 1490 sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 324 324 1620 **But not over a long period of time.** What I mean is that that after some hours running that command again shows how actually the number of processes raises. That's because some of them never get actually closed. sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 324 324 1620 And after some hours this is the result: sosepe@pgbouncer:~$ ps -o pid,user,%mem,command ax | sort -b -k3 -r | grep -o sshd | wc 1926 1926 9630 And these are the consequences: Private + Shared = RAM used Program 4.0 KiB + 22.0 KiB = 26.0 KiB agetty 132.0 KiB + 27.5 KiB = 159.5 KiB vnstatd 128.0 KiB + 45.5 KiB = 173.5 KiB systemd-udevd 136.0 KiB + 65.0 KiB = 201.0 KiB cron 216.0 KiB + 33.0 KiB = 249.0 KiB tail 112.0 KiB + 239.5 KiB = 351.5 KiB systemd-timesyncd 504.0 KiB + 50.0 KiB = 554.0 KiB lvmetad 192.0 KiB + 481.5 KiB = 673.5 KiB vsftpd 908.0 KiB + 92.0 KiB = 1.0 MiB sudo 916.0 KiB + 103.0 KiB = 1.0 MiB pgbouncer 644.0 KiB + 604.0 KiB = 1.2 MiB vmtoolsd 1.3 MiB + 47.0 KiB = 1.3 MiB rsyslogd 1.2 MiB + 247.0 KiB = 1.5 MiB CloudEndure_Age (4) 1.4 MiB + 81.0 KiB = 1.5 MiB dbus-daemon 1.6 MiB + 331.0 KiB = 1.9 MiB su (4) 1.2 MiB + 892.0 KiB = 2.1 MiB VGAuthService 1.7 MiB + 582.0 KiB = 2.2 MiB collectd 2.7 MiB + 268.0 KiB = 3.0 MiB systemd-logind 2.9 MiB + 63.5 KiB = 3.0 MiB bash 4.3 MiB + 231.5 KiB = 4.5 MiB systemd-journald 2.7 MiB + 3.6 MiB = 6.2 MiB php-fpm7.3 (3) 4.8 MiB + 1.8 MiB = 6.6 MiB (sd-pam) (3) 6.5 MiB + 3.3 MiB = 9.8 MiB systemd (4) 5.8 MiB + 4.1 MiB = 9.9 MiB php-fpm7.2 (3) 5.7 MiB + 6.5 MiB = 12.2 MiB php-fpm5.6 (3) 16.1 MiB + 153.0 KiB = 16.3 MiB run_linux_migration_scripts_periodically (2) 17.2 MiB + 166.5 KiB = 17.3 MiB update_onprem_volumes (2) 18.5 MiB + 145.5 KiB = 18.6 MiB tailer (2) 11.8 MiB + 13.1 MiB = 24.9 MiB apache2 (11) 159.3 MiB + 180.0 KiB = 159.5 MiB java 741.6 MiB + 2.1 GiB = 2.8 GiB sshd (4469) --------------------------------- 3.1 GiB ================================= SSHD ate almost 3 GB of memory, and this goes on until the machine is rebooted. Any clue about where the problem could be? Thanks! P.S. This is the conf file: Port 10110 Protocol 1,2 HostKey /etc/ssh/ssh_host_rsa_key HostKey /etc/ssh/ssh_host_ecdsa_key HostKey /etc/ssh/ssh_host_ed25519_key UsePrivilegeSeparation yes SyslogFacility AUTHPRIV LogLevel INFO PermitRootLogin no StrictModes yes RSAAuthentication yes PubkeyAuthentication yes MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160 Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256,diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521 KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521 PermitEmptyPasswords no PasswordAuthentication yes ChallengeResponseAuthentication no UsePAM yes GatewayPorts yes ClientAliveInterval 600 PermitTunnel yes MaxSessions 50 AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE AcceptEnv XMODIFIERS Subsystem sftp /usr/libexec/openssh/sftp-server