CVE-2020-25684

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.

• CWE-358

• https://bugzilla.redhat.com/show_bug.cgi?id=1889686Issue Tracking, Patch, Third Party Advisory
• https://lists.debian.org/debian-lts-announce/2021/03/msg00027.htmlMailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/
• https://security.gentoo.org/glsa/202101-17Third Party Advisory
• https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61Third Party Advisory
• https://www.debian.org/security/2021/dsa-4844Third Party Advisory
• https://www.jsof-tech.com/disclosures/dnspooq/Third Party Advisory
• https://bugzilla.redhat.com/show_bug.cgi?id=1889686Issue Tracking, Patch, Third Party Advisory
• https://lists.debian.org/debian-lts-announce/2021/03/msg00027.htmlMailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/
• https://security.gentoo.org/glsa/202101-17Third Party Advisory
• https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61Third Party Advisory
• https://www.debian.org/security/2021/dsa-4844Third Party Advisory
• https://www.jsof-tech.com/disclosures/dnspooq/Third Party Advisory
• https://www.kb.cert.org/vuls/id/434904

Published

Jan 20, 2021

Last Modified

Jun 17, 2026

Status

Modified