NTP Bug 3377

NTP-01-002 NTP: Buffer Overflow in ntpq when fetching reslist from a malicious ntpd (Medium)

  • Date Resolved: 21 Mar 2017
  • References: Sec 3377 / CVE-2017-6460 / VU#325339
  • Affects: All versions of ntpq, up to but not including ntp-4.2.8p10, and ntp-4.3.0 up to, but not including ntp-4.3.94.
  • CVSS2: MED 4.9 (AV:N/AC:H/Au:S/C:N/I:N/A:C)
  • CVSS3: MED 4.2 CVSS:3.0/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H
  • Summary: A stack buffer overflow in ntpq can be triggered by a malicious ntpd server when ntpq requests the restriction list from the server. This is due to a missing length check in the reslist() function. It occurs whenever the function parses the server’s response and encounters a flagstr variable of an excessive length. The string will be copied into a fixed-size buffer, leading to an overflow on the function’s stack-frame. Note well that this problem requires a malicious server, and affects ntpq, not ntpd.
  • Mitigation:
    • Upgrade to 4.2.8p10, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page
    • If you can't upgrade your version of ntpq then if you want to know the reslist of an instance of ntpd that you do not control, know that if the target ntpd is malicious that it can send back a response that intends to crash your ntpq process.
  • Credit: This weakness was discovered by Cure53.

This topic: Main > SecurityNotice > NtpBug3377
Topic revision: r1 - 2017-03-22 - 01:40:02 - HarlanStenn
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