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-4.2.8p15 was released on 23 June 2020. It addresses 1 medium-severity security issue in ntpd, and provides 13 non-security bugfixes over 4.2.8p13.

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

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NTP Bug 3361

0rigin DoS (Medium)

• Date Resolved: 21 Mar 2017
• References: Sec 3361 / CVE-2016-9042 / VU#325339
• Affects: ntp-4.2.8p9 (21 Nov 2016), up to but not including ntp-4.2.8p10
• CVSS2: MED 4.9 (AV:N/AC:H/Au:N/C:N/I:N/A:C) (worst case)
• CVSS3: MED 4.4 CVSS:3.0/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H (worst case)
• Summary: An exploitable denial of service vulnerability exists in the origin timestamp check functionality of ntpd 4.2.8p9. A specially crafted unauthenticated network packet can be used to reset the expected origin timestamp for target peers. Legitimate replies from targeted peers will fail the origin timestamp check (TEST2) causing the reply to be dropped and creating a denial of service condition. This vulnerability can only be exploited if the attacker can spoof all of the servers.
• Mitigation:
  • Implement BCP-38.
  • Configure enough servers/peers that an attacker cannot target all of your time sources.
  • Upgrade to 4.2.8p10, 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.