A flaw was found in dnsmasq in versions before 2.85. When configured to use a specific server for a given network interface, dnsmasq uses a fixed port while forwarding queries. An attacker on the network, able to find the outgoing port used by dnsmasq, only needs to guess the random transmission ID to forge a reply and get it accepted by dnsmasq. This flaw makes a DNS Cache Poisoning attack much easier. The highest threat from this vulnerability is to data integrity.
Exploitability
AV:NAC:HPR:NUI:NScope
S:CImpact
C:NI:LA:N4/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:NOther