OpenTTD before 1.1.5 contains a Denial of Service (slow read attack) that prevents users from joining the server.
https://security-tracker.debian.org/tracker/CVE-2012-0049
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2012-0049
http://www.openwall.com/lists/oss-security/2012/01/13/9