An exploitable vulnerability exists in the message authentication functionality of libntp in ntp 4.2.8p4 and NTPSec a5fb34b9cc89b92a8fef2f459004865c93bb7f92. An attacker can send a series of crafted messages to attempt to recover the message digest key.
http://lists.fedoraproject.org/pipermail/package-announce/2016-May/183647.html
http://lists.fedoraproject.org/pipermail/package-announce/2016-May/184669.html
http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00034.html
http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00037.html
http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00052.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00001.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00020.html
http://lists.opensuse.org/opensuse-security-announce/2016-07/msg00026.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00042.html
http://lists.opensuse.org/opensuse-updates/2016-05/msg00114.html
http://packetstormsecurity.com/files/136864/Slackware-Security-Advisory-ntp-Updates.html
http://rhn.redhat.com/errata/RHSA-2016-1552.html
https://access.redhat.com/errata/RHSA-2016:1141
https://cert-portal.siemens.com/productcert/pdf/ssa-211752.pdf
https://cert-portal.siemens.com/productcert/pdf/ssa-497656.pdf
https://security.FreeBSD.org/advisories/FreeBSD-SA-16:16.ntp.asc
https://security.gentoo.org/glsa/201607-15
https://security.netapp.com/advisory/ntap-20171004-0002/
https://us-cert.cisa.gov/ics/advisories/icsa-21-103-11
https://us-cert.cisa.gov/ics/advisories/icsa-21-159-11
https://www.debian.org/security/2016/dsa-3629
https://www.kb.cert.org/vuls/id/718152
https://www.talosintelligence.com/vulnerability_reports/TALOS-2016-0084
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160428-ntpd
http://www.debian.org/security/2016/dsa-3629
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
http://www.securitytracker.com/id/1035705