A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in the forward.c:reply_query() if the reply destination address/port is used by the pending forwarded queries. However, it does not use the address/port to retrieve the exact forwarded query, substantially reducing the number of attempts an attacker on the network would have to perform to forge a reply and get it accepted by dnsmasq. This issue contrasts with RFC5452, which specifies a query's attributes that all must be used to match a reply. This flaw allows an attacker to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25685 or CVE-2020-25686, the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.

Affected Software

CPE Name Name Version
thekelleys:dnsmasq thekelleys dnsmasq 2.83
fedoraproject:fedora fedoraproject fedora 32
fedoraproject:fedora fedoraproject fedora 33
debian:debian_linux debian debian linux 9.0
debian:debian_linux debian debian linux 10.0
arista:eos arista eos 4.21.14m
arista:eos arista eos 4.22.9m
arista:eos arista eos 4.23.7m
arista:eos arista eos 4.24.5m
arista:eos arista eos 4.25.2f