r1 - 2016-04-27 - 02:29:54 - HarlanStennYou are here: NTP >  Main Web > SecurityNotice > NtpBug2978
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 2978

Interleave-pivot

  • Date Resolved: Stable (4.2.8p7) 26 Apr 2016; Dev (4.3.92) 26 Apr 2016
  • References: Sec 2978 / CVE-2016-1548 / VU#718152
  • Affects: All ntp-4 releases up to, but not including 4.2.8p7, and 4.3.0 up to, but not including 4.3.92
  • CVSS2: MED 6.4 - (AV:N/AC:L/Au:N/C:N/I:P/A:P)
  • CVSS3: MED 7.2 - CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:L
  • Summary: It is possible to change the time of an ntpd client or deny service to an ntpd client by forcing it to change from basic client/server mode to interleaved symmetric mode. An attacker can spoof a packet from a legitimate ntpd server with an origin timestamp that matches the peer->dst timestamp recorded for that server. After making this switch, the client will reject all future legitimate server responses. It is possible to force the victim client to move time after the mode has been changed. ntpq gives no indication that the mode has been switched.
  • Mitigation:
  • Credit: This weakness was discovered by Miroslav Lichvar of RedHat and separately by Jonathan Gardner of Cisco ASIG.
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