Algorithmic complexity vulnerability in Gem::Version::VERSION_PATTERN in lib/rubygems/version.rb in RubyGems before 1.8.23.1 1.8.24 through 1.8.25 2.0.x before 2.0.8 and 2.1.x before 2.1.0 as used in Ruby 1.9.0 through 2.0.0p247 allows remote attackers to cause a denial of service (CPU consumption) via a crafted gem version that triggers a large amount of backtracking in a regular expression.