OpenTTD 0.3.5 through 1.1.4 allows remote attackers to cause a denial of service (game pause) by connecting to the server and not finishing the (1) authorization phase or (2) map download, aka a "slow read" attack.
Buffer overflow in the TruncateString function in src/gfx.cpp in OpenTTD before 0.6.2 allows remote attackers to cause a denial of service (daemon crash) or possibly execute arbitrary code via a crafted string. NOTE: some of these details are obtained from third party information.