systemd-resolved through 233 allows remote attackers to cause a denial of service (daemon crash) via a crafted DNS response with an empty question section.
https://launchpad.net/bugs/1621396
https://github.com/systemd/systemd/pull/5998
https://github.com/systemd/systemd/commit/a924f43f30f9c4acaf70618dd2a055f8b0f166be