A flaw was found in dnsmasq before version 2.83. When receiving a query dnsmasq does not check for an existing pending request for the same name and forwards a new request. By default a maximum of 150 pending queries can be sent to upstream servers so there can be at most 150 queries for the same name. This flaw allows an off-path attacker on the network to substantially reduce the number of attempts that it would have to perform to forge a reply and have it accepted by dnsmasq. This issue is mentioned in the "Birthday Attacks" section of RFC5452. If chained with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.

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dnsmasq: multiple queries forwarded for the same name makes forging replies easier for an off-path attacker

A flaw was found in dnsmasq. When receiving a query, dnsmasq does not check for an existing pending request for the same name and forwards a new request. By default, a maximum of 150 pending queries can be sent to upstream servers, so there can be at most 150 queries for the same name. This flaw...