This vulnerability was the cause of a record-sized NTP reflection attack in late 2013 and early 2014. We consider this a zero-day vulnerability as it was exploited in the wild before the official patch release.
Vulnerable component: ntp
CVSSv3 score: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:F/RL:O/RC:C
CWE-ID: CWE-20 - Improper Input Validation
The vulnerability allows a remote attacker to cause DoS conditions on the target system.
The weakness exists due to an error in the monlist feature in ntp_request.c. By sending a specially crafted REQ_MON_GETLIST or REQ_MON_GETLIST_1 request, a remote attacker can consume available CPU resources and cause the server to crash.
Successful exploitation of the vulnerability results in denial of service on the vulnerable system.
Note: the vulnerability was being actively exploited.
- NTP ntpd monlist Query Reflection - Denial of Service [Exploit-DB]