systemd-tmpfiles in systemd through 237 mishandles symlinks present in non-terminal path components, which allows local users to obtain ownership of arbitrary files via vectors involving creation of a directory and a file under that directory, and later replacing that directory with a symlink. This occurs even if the fs.protected_symlinks sysctl is turned on.
https://usn.ubuntu.com/3816-2/
https://usn.ubuntu.com/3816-1/
http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00062.html