r1 - 2016-01-20 - 11:34:08 - HarlanStennYou are here: NTP >  Main Web > SecurityNotice > NtpBug2940
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-4.2.8p12 was released on 14 August 2018. It addresses 1 low-/medium-severity security issue in ntpd, 1 low-severity security issue in ntpq and ntpdc, and provides 27 non-security bugfixes and 4 other improvements over 4.2.8p11.

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 2940

Stack exhaustion in recursive traversal of restriction list

  • Date Resolved: Stable (4.2.8p6) 19 Jan 2016; Dev (4.3.90) 19 Jan 2016
  • References: Sec 2940 / CVE-2015-7978
  • Affects: All ntp-4 releases up to, but not including 4.2.8p6, and 4.3.0 up to, but not including 4.3.90
  • CVSS: (AV:N/AC:M/Au:N/C:N/I:N/A:P) Base Score: 4.3
  • Summary: An unauthenticated ntpdc reslist command can cause a segmentation fault in ntpd by exhausting the call stack.
  • Mitigation:
    • Implement BCP-38.
    • Upgrade to 4.2.8p5, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page.
    • If you are unable to upgrade:
      • In ntp-4.2.8, mode 7 is disabled by default. Don't enable it.
      • If you must enable mode 7:
        • configure the use of a requestkey to control who can issue mode 7 requests.
        • configure restrict noquery to further limit mode 7 requests to trusted sources.
    • Monitor your ntpd instances.
  • Credit: This weakness was discovered by Stephen Gray <stepgray@cisco.com> of Cisco ASIG.
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