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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2011-3187
• https://bugzilla.novell.com/show_bug.cgi?id=673010
• http://webservsec.blogspot.com/2011/02/ruby-on-rails-vulnerability.html
• http://www.openwall.com/lists/oss-security/2011/08/17/1
• http://www.openwall.com/lists/oss-security/2011/08/19/11
• http://www.openwall.com/lists/oss-security/2011/08/20/1
• http://www.openwall.com/lists/oss-security/2011/08/22/13
• http://www.openwall.com/lists/oss-security/2011/08/22/14
• http://www.openwall.com/lists/oss-security/2011/08/22/5
• https://github.com/rubysec/ruby-advisory-db/blob/master/gems/actionpack/CVE-2011-3187.yml
• https://web.archive.org/web/20111209181000/http://archives.neohapsis.com/archives/fulldisclosure/2011-02/0337.html