CVE-2020-25685: Arista Eos

Low severity, CVSS 3.7. EPSS: 2.2% chance of exploitation in the next 30 days.

A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. 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.