actionpack/lib/action_dispatch/http/mime_type.rb in Action Pack in Ruby on Rails before 3.2.22.1, 4.0.x and 4.1.x before 4.1.14.1, 4.2.x before 4.2.5.1, and 5.x before 5.0.0.beta1.1 does not properly restrict use of the MIME type cache, which allows remote attackers to cause a denial of service (memory consumption) via a crafted HTTP Accept header.
lists.fedoraproject.org/pipermail/package-announce/2016-February/178043.html
lists.fedoraproject.org/pipermail/package-announce/2016-February/178067.html
lists.opensuse.org/opensuse-security-announce/2016-04/msg00053.html
lists.opensuse.org/opensuse-updates/2016-02/msg00034.html
lists.opensuse.org/opensuse-updates/2016-02/msg00043.html
rhn.redhat.com/errata/RHSA-2016-0296.html
www.debian.org/security/2016/dsa-3464
www.openwall.com/lists/oss-security/2016/01/25/9
www.securityfocus.com/bid/81800
www.securitytracker.com/id/1034816
groups.google.com/forum/message/raw?msg=ruby-security-ann/9oLY_FCzvoc/5CDXbvpYEgAJ