Ruby Memory allocation failure in Ruby regex engine (remotely exploitable DoS)

The regular expression engine (regex.c) in Ruby 1.8.5 and earlier, 1.8.6
through 1.8.6-p286, 1.8.7 through 1.8.7-p71, and 1.9 through r18423 allows
remote attackers to cause a denial of service (infinite loop and crash) via
multiple long requests to a Ruby socket, related to memory allocation
failure, and as demonstrated against Webrick.