NTP users are strongly urged to take immediate action to ensure that their NTP daemons are not susceptible to being used in distributed denial-of-service (DDoS) attacks. Please also take this opportunity to defeat denial-of-service attacks by implementing Ingress and Egress filtering through BCP38.

ntp-4.2.8p9 was released on 21 November 2016. It addresses 1 high- (Windows only), 2 medum-, 2 medum-/low-, and 5 low-severity security issues, 28 bugfixes, and contains other improvements over 4.2.8p8.

Please see the NTP Security Notice for vulnerability and mitigation details.

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NTP Bug 3110

Windows: ntpd DoS by oversized UDP packet

• Date Resolved: 21 Nov 2016
• References: Sec 3110 / CVE-2016-9312 / VU#633847
• Affects: Windows only: ntp-4.?.?, up to but not including ntp-4.2.8p9, and ntp-4.3.0 up to, but not including ntp-4.3.94.
• CVSS2: HIGH 7.8 (AV:N/AC:L/Au:N/C:N/I:N/A:C)
• CVSS3: HIGH 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Summary: If a vulnerable instance of ntpd on Windows receives a crafted malicious packet that is "too big", ntpd will stop working.
• Mitigation:
  • Implement BCP-38.
  • Implement a firewall rule blocking oversized NTP packets.
  • Upgrade to 4.2.8p9, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page
  • Properly monitor your ntpd instances, and auto-restart ntpd (without -g) if it stops running.
• Credit: This weakness was discovered by Robert Pajak of ABB.