In Wireshark 2.6.0 to 2.6.1 and 2.4.0 to 2.4.7, the CoAP protocol dissector could crash. This was addressed in epan/dissectors/packet-coap.c by properly checking for a NULL condition.
https://www.wireshark.org/security/wnpa-sec-2018-42.html
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=14966
http://www.securitytracker.com/id/1041608
http://www.securityfocus.com/bid/104847
http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00027.html