Improperly Implemented Security Check for Standard Affecting dnsmasq package, versions <2.82-1ubuntu2


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.44% (75th percentile)

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  • Snyk IDSNYK-UBUNTU2204-DNSMASQ-2790806
  • published19 Jan 2021
  • disclosed20 Jan 2021

Introduced: 19 Jan 2021

CVE-2020-25685  (opens in a new tab)
CWE-358  (opens in a new tab)

How to fix?

Upgrade Ubuntu:22.04 dnsmasq to version 2.82-1ubuntu2 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream dnsmasq package and not the dnsmasq package as distributed by Ubuntu. See How to fix? for Ubuntu:22.04 relevant fixed versions and status.

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.

CVSS Scores

version 3.1