CVE-2020-25685 Information

Description

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 Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Reference

https://www.jsof-tech.com/disclosures/dnspooq/ https://bugzilla.redhat.com/show_bug.cgi?id=1889688 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/ https://security.gentoo.org/glsa/202101-17 https://www.debian.org/security/2021/dsa-4844 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/ https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

LOW

Base Score

NONE

Base Severity

3.7