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.
https://www.exploit-db.com/exploits/7520
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A9987
http://www.ubuntu.com/usn/usn-696-1
http://www.securityfocus.com/bid/32825
http://www.openwall.com/lists/oss-security/2008/12/14/1
http://www.debian.org/security/2008/dsa-1690
http://security.gentoo.org/glsa/glsa-200901-11.xml
http://secunia.com/advisories/33475
http://secunia.com/advisories/33279
http://secunia.com/advisories/33220
http://secunia.com/advisories/33153
http://lists.opensuse.org/opensuse-security-announce/2009-02/msg00000.html