r1 - 2015-10-23 - 09:26:52 - HarlanStennYou are here: NTP >  Main Web > SecurityNotice > NtpBug2922
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 2922

decodenetnum() will ASSERT botch instead of returning FAIL on some bogus values.

  • Date Resolved: Stable (4.2.8p4) 21 Oct 2015
  • References: Sec 2922 / CVE-2015-7855
  • Affects: All ntp-4 releases up to, but not including 4.2.8p4, and 4.3.0 up to, but not including 4.3.77
  • CVSS: (AV:N/AC:H/Au:M/C:N/I:N/A:C) Base Score: 4.6, worst case
  • Summary: If ntpd is fed a crafted mode 6 or mode 7 packet containing an unusually long data value where a network address is expected, the decodenetnum() function will abort with an assertion failure instead of simply returning a failure condition.
  • Mitigation:
    • Implement BCP-38.
    • Upgrade to 4.2.8p4, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page.
    • If you are unable to upgrade:
      • mode 7 is disabled by default. Don't enable it.
      • Use restrict noquery to limit who can send mode 6 and mode 7 requests.
      • Configure and use the controlkey and requestkey authentication directives to limit who can send mode 6 and mode 7 requests.
    • Monitor your ntpd instances.
  • Credit: This weakness was discovered by John D "Doug" Birdwell with the Institute for Defense Analyses (IDA.org).
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