On Alpine servers that allow password logins, a password over 256 bytes can open accounts that have none.
Alpine SSH bypass: a 257-byte password opens key-only accounts
- OpenSSH 10.6p2 and Alpine's patched packages, out November 5, close the hole for every Alpine release from 3.16 to edge.
What you can do with this
On each Alpine machine running sshd, run apk upgrade -U -a, then rc-service sshd restart. If you cannot update today, set PasswordAuthentication no. Either step closes the bypass.