CVE-2020-25685

Publication date 19 January 2021

Last updated 24 July 2024

Ubuntu priority

Cvss 3 Severity Score

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.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
dnsmasq	24.10 oracular	Fixed 2.82-1ubuntu2
	24.04 LTS noble	Fixed 2.82-1ubuntu2
	23.10 mantic	Fixed 2.82-1ubuntu2
	23.04 lunar	Fixed 2.82-1ubuntu2
	22.10 kinetic	Fixed 2.82-1ubuntu2
	22.04 LTS jammy	Fixed 2.82-1ubuntu2
	21.10 impish	Fixed 2.82-1ubuntu2
	21.04 hirsute	Fixed 2.82-1ubuntu2
	20.10 groovy	Fixed 2.82-1ubuntu1.1
	20.04 LTS focal	Fixed 2.80-1.1ubuntu1.2
	18.04 LTS bionic	Fixed 2.79-1ubuntu0.2
	16.04 LTS xenial	Fixed 2.75-1ubuntu0.16.04.7
	14.04 LTS trusty	Needs evaluation

Severity score breakdown

Parameter	Value
Base score	3.7 · Low
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

References

Related Ubuntu Security Notices (USN)