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 <> of Cisco ASIG.

This topic: Main > SecurityNotice > NtpBug2938
Topic revision: r1 - 2016-01-20 - 11:37:33 - HarlanStenn
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