NTP before 4.2.8p9 does not properly perform the initial sync calculations, which allows remote attackers to unspecified impact via unknown vectors, related to a "root distance that did not include the peer dispersion."
https://www.kb.cert.org/vuls/id/633847
https://us-cert.cisa.gov/ics/advisories/icsa-21-159-11
https://security.FreeBSD.org/advisories/FreeBSD-SA-16:39.ntp.asc
https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03706en_us
https://cert-portal.siemens.com/productcert/pdf/ssa-211752.pdf
https://bto.bluecoat.com/security-advisory/sa139
http://www.ubuntu.com/usn/USN-3349-1
http://www.securitytracker.com/id/1037354
http://www.securityfocus.com/bid/94455
http://www.securityfocus.com/archive/1/archive/1/540254/100/0/threaded
http://www.securityfocus.com/archive/1/archive/1/539955/100/0/threaded
http://www.securityfocus.com/archive/1/540254/100/0/threaded
http://www.securityfocus.com/archive/1/539955/100/0/threaded
http://www.oracle.com/technetwork/security-advisory/cpuoct2017-3236626.html
http://www.huawei.com/en/psirt/security-advisories/huawei-sa-20171129-01-ntpd-en
http://support.ntp.org/bin/view/Main/SecurityNotice#Recent_Vulnerabilities
http://support.ntp.org/bin/view/Main/NtpBug3067
http://rhn.redhat.com/errata/RHSA-2017-0252.html
http://nwtime.org/ntp428p9_release/
http://lists.opensuse.org/opensuse-updates/2016-12/msg00153.html