RubyGems validates versions with a regular expression that is vulnerable to denial of service due to backtracking. For specially crafted RubyGems versions attackers can cause denial of service through CPU consumption. RubyGems versions 2.0.7 and older, 2.1.0.rc.1 and 2.1.0.rc.2 are vulnerable. Ruby versions 1.9.0 through 2.0.0p247 are vulnerable as they contain embedded versions of RubyGems. It does not appear to be possible to exploit this vulnerability by installing a gem for RubyGems 1.8.x or 2.0.x. Vulnerable uses of RubyGems API include packaging a gem (through `gem build`, Gem::Package or Gem::PackageTask), sending user input to Gem::Version.new, Gem::Version.correct? or use of the Gem::Version::VERSION_PATTERN or Gem::Version::ANCHORED_VERSION_PATTERN constants. Notably, users of bundler that install gems from git are vulnerable if a malicious author changes the gemspec to an invalid version. The vulnerability can be fixed by changing the first grouping to an atomic grouping in Gem::Version::VERSION_PATTERN in lib/rubygems/version.rb. For RubyGems 2.0.x: - VERSION_PATTERN = '[0-9]+(\.[0-9a-zA-Z]+)*(-[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?' # :nodoc: + VERSION_PATTERN = '[0-9]+(?>\.[0-9a-zA-Z]+)*(-[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?' # :nodoc: For RubyGems 1.8.x: - VERSION_PATTERN = '[0-9]+(\.[0-9a-zA-Z]+)*' # :nodoc: + VERSION_PATTERN = '[0-9]+(?>\.[0-9a-zA-Z]+)*' # :nodoc: This vulnerability was discovered by Damir Sharipov <dammer2k () gmail com> The above information is also posted at: http://blog.rubygems.org/2013/09/09/CVE-2013-4287.html Patches were committed for: RubyGems 2.1.0.rc.2, released as RubyGems 2.1.0: https://github.com/rubygems/rubygems/commit/938a7e31ac73655845ab9045629ff3f580a125da RubyGems 2.0.7, released as RubyGems 2.0.8: https://github.com/rubygems/rubygems/commit/b9baec03145aed684d1cd3c87dcac3cc06becd9b RubyGems 1.8.25, released as RubyGems 1.8.26: https://github.com/rubygems/rubygems/commit/ed733bc379d75620f5be4213f89d1d7b38be3191 RubyGems 1.8.23, released as RubyGems 1.8.23.1: https://github.com/rubygems/rubygems/commit/b697536f2455e8c8853cf5cf8a1017a36031ed67 The following program can be used to test if you are vulnerable to CVE-2013-4287: