OpenTTD is a clone of Transport Tycoon Deluxe.
OpenTTD is vulnerable to a Denial of Service attack due to a flaw in the manner the game server handles errors in command packets.
An authenticated attacker can cause a Denial of Service by sending an invalid error number to a vulnerable OpenTTD server.
There is no known workaround at this time.
All OpenTTD users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=games-simulation/openttd-0.4.8"