Avahi: Denial of service

Background

Avahi is a system that facilitates service discovery on a local network.

Description

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.

Impact

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.

Workaround

There is no known workaround at this time.

Resolution

All Avahi users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=net-dns/avahi-0.6.24-r2"