Ruby on rails 3.0.5 Remote_IP.rb Input Validation in rails/actionpack

The to_s method in actionpack/lib/action_dispatch/middleware/remote_ip.rb
in Ruby on Rails 3.0.5 does not validate the X-Forwarded-For header
in requests from IP addresses on a Class C network, which might allow
remote attackers to inject arbitrary text into log files or bypass
intended address parsing via a crafted header.