The "pidfile" or "driftfile" directives in NTP ntpd 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77, when ntpd is configured to allow remote configuration, allows remote attackers with an IP address that is allowed to send configuration requests, and with knowledge of the remote configuration password to write to arbitrary files via the :config command.
https://security.netapp.com/advisory/ntap-20171004-0001/
https://security.gentoo.org/glsa/201607-15
https://bugzilla.redhat.com/show_bug.cgi?id=1254547
http://www.securitytracker.com/id/1033951
http://www.securityfocus.com/bid/77278
http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
http://www.debian.org/security/2015/dsa-3388
http://support.ntp.org/bin/view/Main/NtpBug2902