CVE-2020-25686: Arista Eos

Low severity, CVSS 3.7. EPSS: 4.9% chance of exploitation in the next 30 days.

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.

Affected products

• Arista Eos: from 4.21, before 4.21.14m (fixed in 4.21.14m); from 4.22, before 4.22.9m (fixed in 4.22.9m); from 4.23, before 4.23.7m (fixed in 4.23.7m); from 4.24, before 4.24.5m (fixed in 4.24.5m); from 4.25, before 4.25.2f (fixed in 4.25.2f)
• Debian Debian Linux: version 10.0 only
• Fedoraproject Fedora: version 32 only; version 33 only
• Thekelleys Dnsmasq: before 2.83 (fixed in 2.83)

Published 2021-01-20. Last modified 2026-06-17.