The default cloud-init configuration, in cloud-init 0.6.2 and newer, included "ssh_deletekeys: 0", disabling cloud-init's deletion of ssh host keys. In some environments, this could lead to instances created by cloning a golden master or template system, sharing ssh host keys, and being able to impersonate one another or conduct man-in-the-middle attacks.

In cloud-init through 19.4, rand_user_password in cloudinit/config/cc_set_passwords.py has a small default pwlen value, which makes it easier for attackers to guess passwords.