The session fixation protection mechanism in cgi_process.rb in Rails 1.2.4, as used in Ruby on Rails, removes the :cookie_only attribute from the DEFAULT_SESSION_OPTIONS constant, which effectively causes cookie_only to be applied only to the first instantiation of CgiRequest, which allows remote attackers to conduct session fixation attacks. NOTE: this is due to an incomplete fix for CVE-2007-5380.

Session fixation vulnerability in Rails before 1.2.4, as used for Ruby on Rails, allows remote attackers to hijack web sessions via unspecified vectors related to "URL-based sessions."