qh_help in Nagios Core version 4.4.1 and earlier is prone to a NULL pointer dereference vulnerability, which allows attacker to cause a local denial-of-service condition by sending a crafted payload to the listening UNIX socket.
https://www.exploit-db.com/exploits/45082/
https://knowledge.opsview.com/v5.4/docs/whats-new
https://knowledge.opsview.com/v5.3/docs/whats-new
https://gist.github.com/fakhrizulkifli/8df4a174158df69ebd765f824bd736b8
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00022.html
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00014.html