The agroot() function in cgraph\obj.c in libcgraph.a in Graphviz 2.39.20160612.1140 has a NULL pointer dereference, as demonstrated by graphml2gv.
http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00065.html
http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00056.html
http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00065.html
http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00054.html