freeciv: denial of service

A denial of service flaw was found in the way the server component of Freeciv, a turn-based, multi-player, X based strategy game, processed certain packets (invalid packets with whole packet length lower than packet header size or syntactically valid packets, but whose processing would lead to an infinite loop). A remote attacker could send a specially-crafted packet that, when processed would lead to freeciv server to terminate (due to memory exhaustion) or become unresponsive (due to excessive CPU use).