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-4.2.8p11 was released on 27 February 2018. It addresses 2 low-/medium-, 1 informational-/medium-, and 2 low-severity security issues in ntpd, 1 medium-severity security issue in ntpq, and provides over 65 non-security bugfixes and other improvements over 4.2.8p10.

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

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NTP Bug 3119

Mode 6 unauthenticated trap information disclosure and DDoS vector

• Date Resolved: 21 Nov 2016
• References: Sec 3119 / CVE-2016-9311 / 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 4.9 (AV:N/AC:H/Au:N/C:N/I:N/A:C)
• CVSS3: MED 4.4 CVSS:3.0/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
• Summary: ntpd does not enable trap service by default. If trap service has been explicitly enabled, an attacker can send a specially crafted packet to cause a null pointer dereference that will crash ntpd, resulting in a denial of service.
• Mitigation:
  • Implement BCP-38.
  • Use "restrict default noquery ..." in your ntp.conf file. Only allow mode 6 queries from trusted networks and hosts.
  • 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.