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-4.2.8p10 was released on 21 March 2017. It addresses 6 medium- and 5 low-severity security issues, 4 informational security topics, 15 bugfixes, and contains other improvements over 4.2.8p9.

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

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NTP Bug 3118

Mode 6 unauthenticated trap information disclosure and DDoS vector

• Date Resolved: 21 Nov 2016
• References: Sec 3118 / CVE-2016-9310 / VU#633847
• Affects: ntp-4.0.90 (21 July 1999), possibly earlier, up to but not including ntp-4.2.8p9, and ntp-4.3.0 up to, but not including ntp-4.3.94.
• CVSS2: MED 6.4 (AV:A/AC:L/Au:N/C:N/I:N/A:P)
• CVSS3: MED 6.5 CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
• Summary: An exploitable configuration modification vulnerability exists in the control mode (mode 6) functionality of ntpd. If, against long-standing BCP recommendations, "restrict default noquery ..." is not specified, a specially crafted control mode packet can set ntpd traps, providing information disclosure and DDoS amplification, and unset ntpd traps, disabling legitimate monitoring. A remote, unauthenticated, network attacker can trigger this vulnerability.
• Mitigation:
  • Implement BCP-38.
  • Use "restrict default noquery ..." in your ntp.conf file.
  • 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 Matthew Van Gundy of Cisco.