A double-free vulnerability in str2host.c in ldns 1.7.0 have unspecified impact and attack vectors.
https://www.nlnetlabs.nl/bugs-script/show_bug.cgi?id=1257
https://euvd.enisa.europa.eu/vulnerability/EUVD-2017-1500
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00000.html