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CVE-2020-25685

A flaw was found in dnsmasq before version 2.83.

Impact

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

VendorProductAffected versions
ThekelleysDnsmasq
before 2.83
FedoraprojectFedora
Versions 32, 33
DebianDebian Linux
Version 10.0
AristaEos
from 4.21 before 4.21.14m
from 4.22 before 4.22.9m
from 4.23 before 4.23.7m
from 4.24 before 4.24.5m
from 4.25 before 4.25.2f

Weakness classification

CWE-326

References