The HTTP/XMLRPC server in Ruby before 1.8.2 uses blocking sockets, which allows attackers to cause a denial of service (blocked connections) via a large amount of data.
Ruby 1.6.x up to 1.6.8, 1.8.x up to 1.8.2, and 1.9.0 development up to 2005-09-01 allows attackers to bypass safe level and taint flag protections and execute disallowed code when Ruby processes a program through standard input (stdin).