r1 - 2015-10-23 - 09:24:26 - HarlanStennYou are here: NTP >  Main Web > SecurityNotice > NtpBug2920
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.

Are you using Autokey in production? If so, please contact Harlan - he's got some questions for you.

NTP Bug 2920

TALOS-CAN-0064: Invalid length data provided by a custom refclock driver could cause a buffer overflow.

  • Date Resolved: Stable (4.2.8p4) 21 Oct 2015
  • References: Sec 2920 / CVE-2015-7853
  • Affects: Potentially all ntp-4 releases running up to, but not including 4.2.8p4, and 4.3.0 up to, but not including 4.3.77 that have custom refclocks
  • CVSS: (AV:L/AC:H/Au:M/C:C/I:C/A:C) Base Score: 0.0 usual case, 5.9 unusual worst case
  • Summary: A negative value for the datalen parameter will overflow a data buffer. NTF's ntpd driver implementations always set this value to 0 and are therefore not vulnerable to this weakness. If you are running a custom refclock driver in ntpd and that driver supplies a negative value for datalen (no custom driver of even minimal competence would do this) then ntpd would overflow a data buffer. It is even hypothetically possible in this case that instead of simply crashing ntpd the attacker could effect a code injection attack.
  • Mitigation:
  • Credit: This weakness was discovered by Yves Younan of Cisco Talos.
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