A double-free vulnerability in parse.c in ldns 1.7.0 have unspecified impact and attack vectors.
https://www.nlnetlabs.nl/bugs-script/show_bug.cgi?id=1256
https://lists.debian.org/debian-lts-announce/2017/11/msg00028.html
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00000.html