2 files changed, 21 insertions, 2 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/static.rb b/actionpack/lib/action_dispatch/middleware/static.rb
index a8d176560c..7f1117009d 100644
--- a/actionpack/lib/action_dispatch/middleware/static.rb
+++ b/actionpack/lib/action_dispatch/middleware/static.rb
@@ -12,7 +12,7 @@ module ActionDispatch
     def match?(path)
       path = path.dup
 
-      full_path = path.empty? ? @root : File.join(@root, escape_glob_chars(unescape_path(path)))
+      full_path = path.empty? ? @root : File.join(@root, escape_glob_chars(clean_path_info(unescape_path(path))))
       paths = "#{full_path}#{ext}"
 
       matches = Dir[paths]
@@ -42,6 +42,25 @@ module ActionDispatch
       path.force_encoding('binary') if path.respond_to? :force_encoding
       path.gsub(/[*?{}\[\]]/, "\\\\\\&")
     end
+
+    private
+
+    PATH_SEPS = Regexp.union(*[::File::SEPARATOR, ::File::ALT_SEPARATOR].compact)
+
+    def clean_path_info(path_info)
+      parts = path_info.split PATH_SEPS
+
+      clean = []
+
+      parts.each do |part|
+        next if part.empty? || part == '.'
+        part == '..' ? clean.pop : clean << part
+      end
+
+      clean.unshift '/' if parts.empty? || parts.first.empty?
+
+      ::File.join(*clean)
+    end
   end
 
   class Static
diff --git a/actionpack/lib/action_pack/version.rb b/actionpack/lib/action_pack/version.rb
index 3dc00b99fe..94af30d8ad 100644
--- a/actionpack/lib/action_pack/version.rb
+++ b/actionpack/lib/action_pack/version.rb
@@ -2,7 +2,7 @@ module ActionPack
   module VERSION #:nodoc:
     MAJOR = 3
     MINOR = 2
-    TINY  = 19
+    TINY  = 20
     PRE   = nil
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join('.')