- It affects Alpine's openssh-server (built without PAM), or openssh-server-pam with UsePAM no, when PasswordAuthentication is enabled. Alpine says every release they checked is affected, 3.16 through 3.24 and edge.
- Fixed openssh packages are out for all of those, including the older 3.16-3.20 releases. Upgrade and restart sshd (rc-service sshd restart). If you can't upgrade yet, set PasswordAuthentication no.
- To check a box: apk info -v openssh-server for the version, and sshd -T | grep -iE 'usepam|passwordauthentication' for the effective config.
- Containers built FROM alpine that run sshd are easy to miss in an inventory. So are the official tiny-cloud images (3.18.11 through 3.24.3), which ship an alpine user with no password and passwordless doas, so a bypass there means root.
- After patching, look in /var/log/messages for sshd lines saying "Accepted password for" an account that has no password.