Avahi is a system that facilitates service discovery on a local network.
Rob Leslie reported that the originates_from_local_legacy_unicast_socket() function in avahi-core/server.c does not account for the network byte order of a port number when processing incoming multicast packets, leading to a multicast packet storm.
A remote attacker could send specially crafted legacy unicast mDNS query packets to the Avahi daemon, resulting in a Denial of Service due to network bandwidth and CPU consumption.
There is no known workaround at this time.
All Avahi users should upgrade to the latest version:
# emerge --sync # emerge --ask --oneshot --verbose ">=net-dns/avahi-0.6.24-r2"