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 3565

Crafted null dereference attack from a trusted source with an authenticated mode 6 packet

• Date Resolved: Stable (4.2.8p13) 07 Mar 2019
• References: Sec 3565 / CVE-2019-8936
• Affects: All ntp-4 releases up to, but not including 4.2.8p13, and 4.3.0 up to, but not including 4.3.94. Resolved in 4.2.8p13 and 4.3.94.
• CVSS2: MED 4.6 - (AV:N/AC:H/Au:M/C:N/I:N/A:C)
• CVSS3: MED 4.2 - (CVSS:3.0/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H)
• Summary: A crafted malicious authenticated mode 6 (ntpq) packet from a permitted network address can trigger a NULL pointer dereference, crashing ntpd. Note that for this attack to work, the sending system must be on an address that the target's ntpd accepts mode 6 packets from, and must use a private key that is specifically listed as being used for mode 6 authorization.
• Mitigation:
  • Use restrict noquery to limit addresses that can send mode 6 queries.
  • Limit access to the private controlkey in ntp.keys .
  • Upgrade to 4.2.8p13, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page.
• Credit: Reported by Magnus Stubman.

• 2019 Mar 07: Public release
• 2019 Feb 19: Release to Advance Security Partners
• 2019 Jan 17: Reported to Advance Notification Partners
• 2019 Jan 15: Reported to NTF