The filesystem implementation in the Linux kernel through 4.8.2 preserves the setgid bit during a setxattr call, which allows local users to gain group privileges by leveraging the existence of a setgid program with restrictions on execute permissions.
git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=073931017b49d9458aa351605b43a7e34598caef
marc.info/?l=linux-fsdevel&m=147162313630259&w=2
rhn.redhat.com/errata/RHSA-2017-0817.html
www.openwall.com/lists/oss-security/2016/08/26/3
www.securityfocus.com/bid/92659
www.securitytracker.com/id/1038201
www.spinics.net/lists/linux-fsdevel/msg98328.html
www.ubuntu.com/usn/USN-3146-1
www.ubuntu.com/usn/USN-3146-2
www.ubuntu.com/usn/USN-3147-1
access.redhat.com/errata/RHSA-2017:1842
access.redhat.com/errata/RHSA-2017:2077
access.redhat.com/errata/RHSA-2017:2669
bugzilla.redhat.com/show_bug.cgi?id=1368938
github.com/torvalds/linux/commit/073931017b49d9458aa351605b43a7e34598caef
source.android.com/security/bulletin/2017-04-01
support.f5.com/csp/article/K31603170?utm_source=f5support&%3Butm_medium=RSS