r1 - 2016-01-20 - 11:37:33 - HarlanStennYou are here: NTP >  Main Web > SecurityNotice > NtpBug2938
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 2938

ntpq saveconfig command allows dangerous characters in filenames

  • Date Resolved: Stable (4.2.8p6) 19 Jan 2016; Dev (4.3.90) 19 Jan 2016
  • References: Sec 2938 / CVE-2015-7976
  • Affects: All ntp-4 releases up to, but not including 4.2.8p6, and 4.3.0 up to, but not including 4.3.90
  • CVSS: (AV:N/AC:L/Au:S/C:N/I:P/A:N) Base Score: 4.0 MEDIUM
  • Summary: The ntpq saveconfig command does not do adequate filtering of special characters from the supplied filename. Note well: The ability to use the saveconfig command is controlled by the restrict nomodify directive, and the recommended default configuration is to disable this capability. If the ability to execute a saveconfig is required, it can easily (and should) be limited and restricted to a known small number of IP addresses.
  • Mitigation:
    • Implement BCP-38.
    • use restrict default nomodify in your ntp.conf file.
    • Upgrade to 4.2.8p5, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page.
    • If you are unable to upgrade:
      • build NTP with configure --disable-saveconfig if you will never need this capability, or
      • use restrict default nomodify in your ntp.conf file. Be careful about what IPs have the ability to send modify requests to ntpd.
    • Monitor your ntpd instances.
    • saveconfig requests are logged to syslog - monitor your syslog files.
  • Credit: This weakness was discovered by Jonathan Gardner <jonagard@cisco.com> of Cisco ASIG.
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