The originates_from_local_legacy_unicast_socket function (avahi-core/server.c) in avahi-daemon in Avahi before 0.6.24 allows remote attackers to cause a denial of service (crash) via a crafted mDNS packet with a source port of 0, which triggers an assertion failure.
The Avahi daemon in Avahi before 0.6.20 allows attackers to cause a denial of service (exit) via empty TXT data over D-Bus, which triggers an assert error.