actionpack/lib/action_dispatch/http/request.rb in Ruby on Rails before 3.0.13, 3.1.x before 3.1.5, and 3.2.x before 3.2.4 does not properly consider differences in parameter handling between the Active Record component and the Rack interface, which allows remote attackers to bypass intended database-query restrictions and perform NULL checks via a crafted request, as demonstrated by certain "[nil]" values, a related issue to CVE-2012-2694.