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-4.2.8p8 was released on 02 June 2016. It addresses 1 high- and 4 low--severity security issues, 4 bugfixes, and contains other improvements over 4.2.8p7.

Please see the NTP Security Notice for vulnerability and mitigation details.

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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.