rails/rails — pull request #10965 by sbeckeriv (2013-06-16 17:27:43+00:00)
Title: Bad HTTP_ACCEPT can cause request.formats to return an array with nil

https://github.com/rails/rails/blob/ccf256d8dcc68d975bbf00780c3b4096f47e29d3/actionpack/lib/action_controller/metal/rendering.rb#L9

With a carefully crafted HTTP_ACCEPT header request.formats will return [nil] causing the error. Much like https://github.com/rails/rails/issues/7774

NoMethodError: undefined method `ref' for nil:NilClass

little of my Stacktrace
[PROJECT_ROOT]/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.13/lib/action_controller/metal/rendering.rb:9:in `block in process_action`
[PROJECT_ROOT]/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.13/lib/action_controller/metal/rendering.rb:9:in `map`
[PROJECT_ROOT]/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.13/lib/action_controller/metal/rendering.rb:9:in `process_action`
[PROJECT_ROOT]/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.13/lib/abstract_controller/callbacks.rb:18:in `block in process_action`
[PROJECT_ROOT]/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/callbacks.rb:469:in `_run__4125533832456839663__process_action__2284511760730381774__callbacks`
[PROJECT_ROOT]/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/callbacks.rb:405:in `__run_callback`
[PROJECT_ROOT]/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks`
[PROJECT_ROOT]/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/callbacks.rb:81:in `run_callbacks`

Could/Should be backported?