Cannot connect to EC2 instance from the beginning

Question

Here is the SSH connection diagnose output:

C:\Users\YYY>ssh -v -i  WebKey.pem ec2-user@ec2-3-80-22-124.compute-1.amazonaws.com
OpenSSH_for_Windows_8.1p1, LibreSSL 3.0.2
debug1: Connecting to ec2-3-80-22-124.compute-1.amazonaws.com [3.80.22.124] port 22.
debug1: Connection established.
debug1: identity file WebKey.pem type -1
debug1: identity file WebKey.pem-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_for_Windows_8.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.4p1 Debian-5+deb11u2
debug1: match: OpenSSH_8.4p1 Debian-5+deb11u2 pat OpenSSH* compat 0x04000000
debug1: Authenticating to ec2-3-80-22-124.compute-1.amazonaws.com:22 as 'ec2-user'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC:  compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC:  compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:8FWlqWo+yY5LyO0BCVYst0sUSfth8/49KEZSwvN1RWg
debug1: read_passphrase: can't open /dev/tty: No such file or directory
The authenticity of host 'ec2-3-80-22-124.compute-1.amazonaws.com (3.80.22.124)' can't be established.
ECDSA key fingerprint is SHA256:8FWlqWo+yY5LyO0BCVYst0sUSfth8/49KEZSwvN1RWg.
Are you sure you want to continue connecting (yes/no/[fingerprint])? no
Host key verification failed.

This output shows it is a problem from the instance side, cannot fix it without login. Anybody had the same issue before?
Thanks.

Answer

> Are you sure you want to continue connecting (yes/no/[fingerprint])?

From the output above it loks like you replied **no** to this, and so the connection terminates.

What happens when you answer yes?

Answer

Which version of Linux is installed on the EC2?

This hints at it being Debian `OpenSSH_8.4p1 Debian-5+deb11u2` and the default user for Debian is **admin** not **ec2-user** https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/managing-users.html#ami-default-user-names

Answer

Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'ec2-3-80-22-124.compute-1.amazonaws.com,3.80.22.124' (ECDSA) to the list of known hosts.
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: pubkey_prepare: ssh_get_authentication_socket: No such file or directory
debug1: Will attempt key: WebKey.pem  explicit
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: WebKey.pem
debug1: Authentications that can continue: publickey
debug1: No more authentication methods to try.
ec2-user@ec2-3-80-22-124.compute-1.amazonaws.com: Permission denied (publickey).

Cannot connect to EC2 instance from the beginning

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