Session fixation vulnerability in the "Remember Me" login feature in Symfony 2.3.x before 2.3.35, 2.6.x before 2.6.12, and 2.7.x before 2.7.7 allows remote attackers to hijack web sessions via a session id.
https://symfony.com/blog/cve-2015-8124-session-fixation-in-the-remember-me-login-feature
http://www.securityfocus.com/bid/77694
http://www.securityfocus.com/archive/1/537183/100/0/threaded
http://www.debian.org/security/2015/dsa-3402
http://seclists.org/fulldisclosure/2015/Dec/89
http://lists.fedoraproject.org/pipermail/package-announce/2015-December/173300.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-December/173271.html