r1 - 2016-01-20 - 11:42:00 - HarlanStennYou are here: NTP >  Main Web > SecurityNotice > NtpBug2946
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-4.2.8p7 was released on 26 April 2016. It addresses 11 low- and medium-severity security issues, 16 bugfixes, and contains other improvements over 4.2.8p6.

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 2946

Origin Leak: ntpq and ntpdc Disclose Origin Timestamp to Unauthenticated Clients

  • Date Resolved: Stable (4.2.8p7) XX Feb 2016; Dev (4.3.XX) XX Feb 2016
  • References: Sec 2546 / CVE-2015-8139
  • Affects: All ntp-4 releases up to, but not including 4.2.8p7, and 4.3.0 up to, but not including 4.3.XX
  • CVSS2: (AV:N/AC:L/Au:N/C:P/I:P/A:N) Base Score: 5.0 - MEDIUM
  • CVSS3: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N) Base Score: 5.3 - MEDIUM
  • Summary: To prevent off-path attackers from impersonating legitimate peers, clients require that the origin timestamp in a received response packet match the transmit timestamp from its last request to a given peer. Under assumption that only the recipient of the request packet will know the value of the transmit timestamp, this prevents an attacker from forging replies.
  • Mitigation:
    • Configure ntpd to get time from multiple sources.
    • Configure ntpd with restrict statements to limit who is allowed to issue ntpq and ntpdc queries. Note that ntpdc queries are disabled by default.
    • Monitor your ntpd instances.
  • Credit: This weakness was discovered by Matthew Van Gundy <mvangund@cisco.com> of Cisco ASIG.
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