The nginx package before 1.6.2-5+deb8u3 on Debian jessie, the nginx packages before 1.4.6-1ubuntu3.6 on Ubuntu 14.04 LTS, before 1.10.0-0ubuntu0.16.04.3 on Ubuntu 16.04 LTS, and before 1.10.1-0ubuntu1.1 on Ubuntu 16.10, and the nginx ebuild before 1.10.2-r3 on Gentoo allow local users with access to the web server user account to gain root privileges via a symlink attack on the error log.
packetstormsecurity.com/files/139750/Nginx-Debian-Based-Distros-Root-Privilege-Escalation.html
seclists.org/fulldisclosure/2016/Nov/78
seclists.org/fulldisclosure/2017/Jan/33
www.debian.org/security/2016/dsa-3701
www.securityfocus.com/archive/1/539796/100/0/threaded
www.securityfocus.com/bid/93903
www.securitytracker.com/id/1037104
www.ubuntu.com/usn/USN-3114-1
legalhackers.com/advisories/Nginx-Exploit-Deb-Root-PrivEsc-CVE-2016-1247.html
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CBIZEKHBOCKO7FUMCO4X53ENMWU5OYFX/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ESTIADC7BDB6VTH4JAP6C6OCW2CQ4NHP/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/P3WOO7E5R2HT5XVOIOFPEFALILVOWZUF/
security.gentoo.org/glsa/201701-22
www.exploit-db.com/exploits/40768/
www.youtube.com/watch?v=aTswN1k1fQs