It was discovered that Mosquitto incorrectly handled certain specially crafted input and network packets. A remote attacker could use this to cause a denial of service. Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
Eclipse Mosquitto Denial Of Service (CVE-2019-11779)
Fedora 29 : mosquitto (2019-d99e2329cb)
Fedora 30 : mosquitto (2019-8b83c261dd)
Fedora 31 : mosquitto (2019-4c69fb4cd7)
openSUSE: Security Advisory for mosquitto (openSUSE-SU-2019:2206-1)
Ubuntu Update for mosquitto USN-4137-1
Debian Security Advisory DSA 4570-1 (mosquitto - security update)