{"id":"CVE-2020-12667","url":"https://www.cyber-defence.io/tools/cve/CVE-2020-12667","generatedAt":"2026-10-27T22:33:38.131Z","title":"Knot Resolver before 5.1.1 allows traffic amplification via a crafted DNS answer from an attacker-controlled server, aka an \"NXNSAttack\" issue.","description":"Knot Resolver before 5.1.1 allows traffic amplification via a crafted DNS answer from an attacker-controlled server, aka an \"NXNSAttack\" issue. This is triggered by random subdomains in the NSDNAME in NS records.","published":"2020-05-19T13:15:12.000Z","lastModified":"2026-06-17T02:52:06.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-400"],"affected":["nic/knot resolver"],"epss":{"score":0.02612,"percentile":0.8531,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (2.61%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"http://cyber-security-group.cs.tau.ac.il/#","tags":["Technical Description","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"http://www.openwall.com/lists/oss-security/2020/05/19/2","tags":["Mailing List","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://en.blog.nic.cz/2020/05/19/nxnsattack-upgrade-resolvers-to-stop-new-kind-of-random-subdomain-attack/","tags":["Technical Description","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://lists.debian.org/debian-lts-announce/2024/04/msg00017.html","source":"cve@mitre.org"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/76Y4FITMOH6RVPWAANGV7NB2ZHPJJGDQ/","source":"cve@mitre.org"},{"url":"https://www.knot-resolver.cz/2020-05-19-knot-resolver-5.1.1.html","tags":["Release Notes","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"http://cyber-security-group.cs.tau.ac.il/#","tags":["Technical Description","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.openwall.com/lists/oss-security/2020/05/19/2","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://en.blog.nic.cz/2020/05/19/nxnsattack-upgrade-resolvers-to-stop-new-kind-of-random-subdomain-attack/","tags":["Technical Description","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2024/04/msg00017.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/76Y4FITMOH6RVPWAANGV7NB2ZHPJJGDQ/","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.knot-resolver.cz/2020-05-19-knot-resolver-5.1.1.html","tags":["Release Notes","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2020-12667","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}