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CVE-2020-25684

Published: 19 January 2021

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.

Priority

Medium

Cvss 3 Severity Score

3.7

Score breakdown

Status

Package Release Status
dnsmasq
Launchpad, Ubuntu, Debian
bionic
Released (2.79-1ubuntu0.2)
hirsute
Released (2.82-1ubuntu2)
lunar
Released (2.82-1ubuntu2)
focal
Released (2.80-1.1ubuntu1.2)
groovy
Released (2.82-1ubuntu1.1)
impish
Released (2.82-1ubuntu2)
jammy
Released (2.82-1ubuntu2)
kinetic
Released (2.82-1ubuntu2)
trusty Needs triage

upstream
Released (2.83)
xenial
Released (2.75-1ubuntu0.16.04.7)
mantic
Released (2.82-1ubuntu2)

Severity score breakdown

Parameter Value
Base score 3.7
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact Low
Availability impact None
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N