NTP before 4.2.8p9 changes the peer structure to the interface it receives the response from a source, which allows remote attackers to cause a denial of service (prevent communication with a source) by sending a response for a source to an interface the source does not use.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:NI:NA:L3.7/CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L