ext/session/session.c in PHP before 5.6.25 and 7.x before 7.0.10 skips invalid session names in a way that triggers incorrect parsing, which allows remote attackers to inject arbitrary-type session data by leveraging control of a session name, as demonstrated by object injection.
openwall.com/lists/oss-security/2016/09/02/9
rhn.redhat.com/errata/RHSA-2016-2750.html
www.php.net/ChangeLog-5.php
www.php.net/ChangeLog-7.php
www.securityfocus.com/bid/92552
www.securitytracker.com/id/1036680
bugs.php.net/bug.php?id=72681
github.com/php/php-src/commit/8763c6090d627d8bb0ee1d030c30e58f406be9ce?w=1
security.gentoo.org/glsa/201611-22
www.tenable.com/security/tns-2016-19