Report on scanning publicly available Docker Hub images for vulnerabilities. It isn’t the first analysis of this kind, but the result is the same: There are still many harmful container images out there.

The basic premise of this attack is that FollowSymlinkInScope suffers
from a fairly fundamental TOCTOU attack. The purpose of
FollowSymlinkInScope is to take a given path and safely resolve it as
though the process was inside the container. After the full path has
been resolved, the resolved path is passed around a bit and then
operated on a bit later (in the case of 'docker cp' it is opened when
creating the archive that is streamed to the client). If an attacker can
add a symlink component to the path after the resolution but before
it is operated on, then you could end up resolving the symlink path
component on the host as root. In the case of 'docker cp' this gives you
read and write access to any path on the host.

Versions of the Official Alpine Linux Docker images (since v3.3) contain a NULL password for the root user.