diff --git a/actionpack/lib/action_dispatch/middleware/static.rb b/actionpack/lib/action_dispatch/middleware/static.rb
index e66c21ef85..002bf8b11a 100644
--- a/actionpack/lib/action_dispatch/middleware/static.rb
+++ b/actionpack/lib/action_dispatch/middleware/static.rb
@@ -24,9 +24,19 @@ module ActionDispatch
       path = URI.parser.unescape(path)
       return false unless path.valid_encoding?
 
-      paths = [path, "#{path}#{ext}", "#{path}/index#{ext}"]
+      paths = [path, "#{path}#{ext}", "#{path}/index#{ext}"].map { |v|
+        Rack::Utils.clean_path_info v
+      }
 
-      if match = paths.detect {|p| File.file?(File.join(@root, p)) }
+      if match = paths.detect { |p|
+        path = File.join(@root, p)
+        begin
+          File.file?(path) && File.readable?(path)
+        rescue SystemCallError
+          false
+        end
+
+      }
         return ::Rack::Utils.escape(match)
       end
     end
diff --git a/actionpack/test/dispatch/static_test.rb b/actionpack/test/dispatch/static_test.rb
index 6f7373201c..7f1207eaed 100644
--- a/actionpack/test/dispatch/static_test.rb
+++ b/actionpack/test/dispatch/static_test.rb
@@ -200,7 +200,8 @@ class StaticTest < ActiveSupport::TestCase
   }
 
   def setup
-    @app = ActionDispatch::Static.new(DummyApp, "#{FIXTURE_LOAD_PATH}/public", "public, max-age=60")
+    @root = "#{FIXTURE_LOAD_PATH}/public"
+    @app = ActionDispatch::Static.new(DummyApp, @root, "public, max-age=60")
   end
 
   def public_path
@@ -208,11 +209,28 @@ class StaticTest < ActiveSupport::TestCase
   end
 
   include StaticTests
+
+  def test_custom_handler_called_when_file_is_outside_root
+    filename = 'shared.html.erb'
+    assert File.exist?(File.join(@root, '..', filename))
+    env = {
+      "REQUEST_METHOD"=>"GET",
+      "REQUEST_PATH"=>"/..%2F#{filename}",
+      "PATH_INFO"=>"/..%2F#{filename}",
+      "REQUEST_URI"=>"/..%2F#{filename}",
+      "HTTP_VERSION"=>"HTTP/1.1",
+      "SERVER_NAME"=>"localhost",
+      "SERVER_PORT"=>"8080",
+      "QUERY_STRING"=>""
+    }
+    assert_equal(DummyApp.call(nil), @app.call(env))
+  end
 end
 
 class StaticEncodingTest < StaticTest
   def setup
-    @app = ActionDispatch::Static.new(DummyApp, "#{FIXTURE_LOAD_PATH}/公共", "public, max-age=60")
+    @root = "#{FIXTURE_LOAD_PATH}/公共"
+    @app = ActionDispatch::Static.new(DummyApp, @root, "public, max-age=60")
   end
 
   def public_path