r1 - 2015-10-23 - 09:22:02 - HarlanStennYou are here: NTP >  Main Web > SecurityNotice > NtpBug2917
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 medum- 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 2917

TALOS-CAN-0055: Infinite loop if extended logging enabled and the logfile and keyfile are the same.

  • Date Resolved: Stable (4.2.8p4) 21 Oct 2015
  • References: Sec 2917 / CVE-2015-7850
  • 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 configured to allow remote configuration, and if the (possibly spoofed) source IP address is allowed to send remote configuration requests, and if the attacker knows the remote configuration password or if ntpd was configured to disable authentication, then an attacker can send a set of packets to ntpd that will cause it to crash and/or create a potentially huge log file. Specifically, the attacker could enable extended logging, point the key file at the log file, and cause what amounts to an infinite loop.
  • 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, remote configuration of NTF's ntpd requires:
      • an explicitly configured "trusted" key. Only configure this if you need it.
      • access from a permitted IP address. You choose the IPs.
      • authentication. Don't disable it. Practice secure key safety.
    • Monitor your ntpd instances.
  • Credit: This weakness was discovered by Yves Younan of Cisco Talos.
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