A response splitting flaw in Ruby on Rails 2.3.x was reported  that could allow a remote attacker to inject arbitrary HTTP headers into a response due to insufficient sanitization of the values provided for response content types.
This is corrected in upstream 2.3.13 (3.0.0 and later are not vulnerable). Patches are available in the advisory  and git .
Created rubygem-actionpack tracking bugs for this issue
Affects: fedora-14 [bug 732158]
Affects: epel-5 [bug 677629]
This issue has been assigned the name CVE-2011-3186:
This issue does not affect the version of rubygem-actionpack shipped with Fedora 15.
This issue has been addressed in Fedora-14 via the following advisory: