ntpd: read_mru_list() does inadequate incoming packet checks

Summary

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.