An issue was discovered in adns before 1.5.2. It hangs, eating CPU, if a compression pointer loop is encountered.
https://www.chiark.greenend.org.uk/pipermail/adns-announce/2020/000004.html
http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=adns.git%3Ba=blob%3Bf=changelog
http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=adns.git
http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00037.html