CVE-2013-0262 rubygem-rack: Path sanitization information disclosure

rack/file.rb (Rack::File) in Rack 1.5.x before 1.5.2 and 1.4.x before
1.4.5 allows attackers to access arbitrary files outside the intended root directory
via a crafted PATH_INFO environment variable, probably a directory traversal vulnerability
that is remotely exploitable, aka “symlink path traversals.”