Directory traversal vulnerability in actionpack/lib/action_dispatch/middleware/static.rb in Action Pack in Ruby on Rails 3.x before 3.2.21 4.0.x before 4.0.12 4.1.x before 4.1.8 and 4.2.x before 4.2.0.beta4 when serve_static_assets is enabled allows remote attackers to determine the existence of files outside the application root via vectors involving a \\ (backslash) character a similar issue to CVE-2014-7818.