The mx4200_send function in the legacy MX4200 refclock in NTP before 4.2.8p10 and 4.3.x before 4.3.94 does not properly handle the return value of the snprintf function, which allows local users to execute arbitrary code via unspecified vectors, which trigger an out-of-bounds memory write.
support.ntp.org/bin/view/Main/NtpBug3378
support.ntp.org/bin/view/Main/SecurityNotice#March_2017_ntp_4_2_8p10_NTP_Secu
www.securityfocus.com/bid/97058
www.securitytracker.com/id/1038123
www.securitytracker.com/id/1039427
support.apple.com/HT208144
support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03962en_us