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 <> of Cisco ASIG.

This topic: Main > SecurityNotice > NtpBug2946
Topic revision: r1 - 2016-01-20 - 11:42:00 - HarlanStenn
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