CVE-2011-3187

CVE-2011-3187 describes an HTTP header injection vulnerability in Ruby on Rails 3.0.5, specifically within the to_s method of actionpack/lib/action_dispatch/middleware/remote_ip.rb. This flaw allows remote attackers to inject arbitrary text into log files or bypass address parsing by crafting the X-Forwarded-For header, particularly when requests originate from Class C network IP addresses. The vulnerability has a CVSS score of 4.3 (Medium severity), indicating a network-based attack with medium complexity and a potential impact on integrity (partial). While there is no evidence of active exploitation (KEV: No), an exploit module for Ruby on Rails 3.0.5 is available on ExploitDB, and the vulnerability has received minimal community discussion or media coverage.