lib/rack/utils.rb in Rack before 1.5.4 and 1.6.x before 1.6.2, as used with Ruby on Rails 3.x and 4.x and other products, allows remote attackers to cause a denial of service (SystemStackError) via a request with a large parameter depth.
https://groups.google.com/forum/message/raw?msg=rubyonrails-security/gcUbICUmKMc/qiCotVZwXrMJ
https://github.com/rack/rack/blob/master/HISTORY.md
http://www.securityfocus.com/bid/75232
http://www.debian.org/security/2015/dsa-3322
http://rhn.redhat.com/errata/RHSA-2015-2290.html
http://openwall.com/lists/oss-security/2015/06/16/14
http://lists.opensuse.org/opensuse-updates/2015-07/msg00044.html
http://lists.opensuse.org/opensuse-updates/2015-07/msg00043.html
http://lists.opensuse.org/opensuse-updates/2015-07/msg00040.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-August/165180.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-August/164173.html