NTP Bug 3082

read_mru_list() does inadequate incoming packet checks

• Date Resolved: 21 Nov 2016
• References: Sec 3082 / CVE-2016-7434 / VU#633847
• Affects: ntp-4.2.7p22, up to but not including ntp-4.2.8p9, and ntp-4.3.0 up to, but not including ntp-4.3.94.
• CVSS2: LOW 3.8 (AV:L/AC:H/Au:S/C:N/I:N/A:C)
• CVSS3: LOW 3.8 CVSS:3.0/AV:P/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H
• Summary: If ntpd is configured to allow mrulist query requests from a server that sends a crafted malicious packet, ntpd will crash on receipt of that crafted malicious mrulist query packet.
• Mitigation:
  • Only allow mrulist query packets from trusted hosts.
  • Implement BCP-38.
  • Upgrade to 4.2.8p9, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page
  • Properly monitor your ntpd instances, and auto-restart ntpd (without -g) if it stops running.
• Credit: This weakness was discovered by Magnus Stubman.