Forwarded: https://gitlab.com/gitlab-org/gitlab-ce/issues/2800

Index: gitlab/Gemfile
===================================================================
--- gitlab.orig/Gemfile
+++ gitlab/Gemfile
@@ -67,7 +67,7 @@ gem "gitlab-linguist", "~> 3.0.1", requi
 # API
 gem "grape", "~> 0.6"
 gem "grape-entity", "~> 0.4.2"
-gem 'rack-cors', '~> 0.2.9', require: 'rack/cors'
+gem 'rack-cors', '~> 0.4.0', require: 'rack/cors'
 
 # Format dates and times
 # based on human-friendly examples