Here is the command I use to boot QEMU:

qemu-system-aarch64 -M virt -m 32768 -cpu cortex-a72 \
  -kernel $VMLINUZ \
  -initrd $INITRD \
  -append 'root=/dev/vda2' \
  -drive if=none,file=$COW,format=qcow2,id=hd \
  -device virtio-blk-pci,drive=hd \
  -netdev user,id=mynet \
  -device virtio-net-pci,netdev=mynet \
  -nographic \
  -device e1000,netdev=net0 \
  -netdev user,id=net0,hostfwd=tcp::5555-:22

Once QEMU is booted, I try to SSH using the following command and get this output:

<*user*>@<*hostname*>:~$ ssh localhost -p 5555 -vvv
OpenSSH_7.6p1 Ubuntu-4ubuntu0.3, OpenSSL 1.0.2n  7 Dec 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "localhost" port 5555
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to localhost [127.0.0.1] port 5555.
debug1: Connection established.
debug1: identity file /home/<*user*>/.ssh/id_rsa type 0
debug1: key_load_public: No such file or directory
debug1: identity file /home/<*user*>/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/<*user*>/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/<*user*>/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/<*user*>/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/<*user*>/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/<*user*>/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/<*user*>/.ssh/id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
ssh_exchange_identification: read: Connection reset by peer

Any help with this is greatly appreciated!

Edit:

Both machines are running Ubuntu 18.04.

Host:

Linux trace5 5.0.0-37-generic #40~18.04.1-Ubuntu SMP Thu Nov 14 12:06:39 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

Guest:

Linux qemu-trace 5.2.0-050200-generic #201907072331 SMP Sun Jul 7 23:48:00 UTC 2019 aarch64 aarch64 aarch64 GNU/Linux

Guest is running sshd,

ps -ef | grep '[s]shd'
root 616 1 0 Dec11 ? 00:00:00 /usr/sbin/sshd -D

This is an excerpt of /var/log/auth.log on the Guest if it helps. I'm reading an authentication failure, but unsure what that means as the timestamps don't align with when my host was ssh-ing:

Dec 11 18:43:17 qemu-trace sshd[1547]: Server listening on 0.0.0.0 port 22.
Dec 11 18:43:17 qemu-trace sshd[1547]: Server listening on :: port 22.
Dec 11 18:43:17 qemu-trace sudo: pam_unix(sudo:session): session closed for user root
Dec 11 18:45:30 qemu-trace systemd-logind[610]: New seat seat0.
Dec 11 18:45:33 qemu-trace sshd[617]: Server listening on 0.0.0.0 port 22.
Dec 11 18:45:33 qemu-trace sshd[617]: Server listening on :: port 22.
Dec 11 18:46:18 qemu-trace login[620]: pam_unix(login:session): session opened for user trace by LOGIN(uid=0)
Dec 11 18:46:19 qemu-trace systemd-logind[610]: New session 1 of user trace.
Dec 11 18:46:19 qemu-trace systemd: pam_unix(systemd-user:session): session opened for user trace by (uid=0)
Dec 11 19:17:01 qemu-trace CRON[675]: pam_unix(cron:session): session opened for user root by (uid=0)
Dec 11 19:17:02 qemu-trace CRON[675]: pam_unix(cron:session): session closed for user root
Dec 11 19:20:13 qemu-trace systemd-logind[605]: New seat seat0.
Dec 11 19:20:17 qemu-trace sshd[616]: Server listening on 0.0.0.0 port 22.
Dec 11 19:20:17 qemu-trace sshd[616]: Server listening on :: port 22.
Dec 11 19:22:33 qemu-trace login[621]: pam_unix(login:auth): check pass; user unknown
Dec 11 19:22:33 qemu-trace login[621]: pam_unix(login:auth): authentication failure; logname=LOGIN uid=0 euid=0 tty=/dev/ttyAMA0 ruser= rhost=
Dec 11 19:22:37 qemu-trace login[621]: FAILED LOGIN (1) on '/dev/ttyAMA0' FOR 'UNKNOWN', Authentication failure
Dec 11 19:22:49 qemu-trace login[621]: pam_unix(login:session): session opened for user trace by LOGIN(uid=0)
Dec 11 19:22:49 qemu-trace systemd-logind[605]: New session 1 of user trace.
Dec 11 19:22:50 qemu-trace systemd: pam_unix(systemd-user:session): session opened for user trace by (uid=0)