{"id":"UBUNTU-CVE-2020-25686","details":"A flaw was found in dnsmasq before version 2.83. When receiving a query, dnsmasq does not check for an existing pending request for the same name and forwards a new request. By default, a maximum of 150 pending queries can be sent to upstream servers, so there can be at most 150 queries for the same name. This flaw allows an off-path attacker on the network to substantially reduce the number of attempts that it would have to perform to forge a reply and have it accepted by dnsmasq. This issue is mentioned in the \"Birthday Attacks\" section of RFC5452. 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.","modified":"2026-05-26T20:00:41.543151429Z","published":"2021-01-19T00:00:00Z","related":["USN-4698-1"],"upstream":["CVE-2020-25686"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2020-25686"},{"type":"REPORT","url":"https://www.jsof-tech.com/disclosures/dnspooq/"},{"type":"REPORT","url":"http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2021q1/014599.html"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-4698-1"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2020-25686"}],"affected":[{"package":{"name":"dnsmasq","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/dnsmasq?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.66-4ubuntu1","2.67-1","2.68-1","2.68-1ubuntu0.1","2.68-1ubuntu0.2","2.68-1ubuntu0.2+esm1","2.68-1ubuntu0.2+esm2","2.68-1ubuntu0.2+esm3","2.68-1ubuntu0.2+esm5","2.68-1ubuntu0.2+esm6"],"ecosystem_specific":{"binaries":[{"binary_version":"2.68-1ubuntu0.2+esm6","binary_name":"dnsmasq"},{"binary_version":"2.68-1ubuntu0.2+esm6","binary_name":"dnsmasq-base"},{"binary_version":"2.68-1ubuntu0.2+esm6","binary_name":"dnsmasq-utils"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2020/UBUNTU-CVE-2020-25686.json"}},{"package":{"name":"dnsmasq","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/dnsmasq?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.75-1ubuntu0.16.04.7"}]}],"versions":["2.75-1","2.75-1ubuntu0.16.04.1","2.75-1ubuntu0.16.04.2","2.75-1ubuntu0.16.04.3","2.75-1ubuntu0.16.04.4","2.75-1ubuntu0.16.04.5"],"ecosystem_specific":{"binaries":[{"binary_version":"2.75-1ubuntu0.16.04.7","binary_name":"dnsmasq"},{"binary_name":"dnsmasq-base","binary_version":"2.75-1ubuntu0.16.04.7"},{"binary_version":"2.75-1ubuntu0.16.04.7","binary_name":"dnsmasq-utils"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2020/UBUNTU-CVE-2020-25686.json"}},{"package":{"name":"dnsmasq","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/dnsmasq?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.79-1ubuntu0.2"}]}],"versions":["2.78-1","2.78-3","2.79-1"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"dnsmasq","binary_version":"2.79-1ubuntu0.2"},{"binary_name":"dnsmasq-base","binary_version":"2.79-1ubuntu0.2"},{"binary_name":"dnsmasq-base-lua","binary_version":"2.79-1ubuntu0.2"},{"binary_name":"dnsmasq-utils","binary_version":"2.79-1ubuntu0.2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2020/UBUNTU-CVE-2020-25686.json"}},{"package":{"name":"dnsmasq","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/dnsmasq?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.80-1.1ubuntu1.2"}]}],"versions":["2.80-1ubuntu2","2.80-1ubuntu4","2.80-1.1ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"dnsmasq","binary_version":"2.80-1.1ubuntu1.2"},{"binary_name":"dnsmasq-base","binary_version":"2.80-1.1ubuntu1.2"},{"binary_version":"2.80-1.1ubuntu1.2","binary_name":"dnsmasq-base-lua"},{"binary_name":"dnsmasq-utils","binary_version":"2.80-1.1ubuntu1.2"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2020/UBUNTU-CVE-2020-25686.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}