Sensitive data could be exposed in logs of cloud-init before version 23.1.2. An attacker could use this information to find hashed passwords and possibly escalate their privilege.

Sensitive data could be exposed in world readable logs of cloud-init before version 22.3 when schema failures are reported. This leak could include hashed passwords.

When instructing cloud-init to set a random password for a new user account, versions before 21.2 would write that password to the world-readable log file /var/log/cloud-init-output.log. This could allow a local user to log in as another user.

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.

cloud-init through 19.4 relies on Mersenne Twister for a random password, which makes it easier for attackers to predict passwords, because rand_str in cloudinit/util.py calls the random.choice function.

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.