{"id":"UBUNTU-CVE-2026-39155","details":"Knot DNS before 3.4.10 and 3.5.x before 3.5.4 contains a vulnerability in mod-onlinesign where the next NSEC owner name can be computed incorrectly. This can create an overly broad authenticated denial interval, allowing downstream validating resolvers using aggressive negative caching to synthesize negative answers for legitimate names and causing resolver-side denial of service.","modified":"2026-07-29T07:55:20Z","published":"2026-07-23T21:17:00Z","upstream":["CVE-2026-39155"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-39155"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-39155"},{"type":"REPORT","url":"https://www.knot-dns.cz/2026-04-01-version-3410.html"},{"type":"REPORT","url":"https://www.knot-dns.cz/2026-04-02-version-354.html"}],"affected":[{"package":{"name":"knot","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/knot?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0-1","2.0.1-4","2.0.1-4build1","2.0.2-1","2.0.2-1build1","2.1.0~rc1-52-gd80ce77-1","2.1.0~rc1-55-gf227348-1","2.1.0-2","2.1.0-3","2.1.1-1","2.1.1-1build1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.1.1-1build1","binary_name":"knot"},{"binary_name":"knot-dnsutils","binary_version":"2.1.1-1build1"},{"binary_name":"knot-host","binary_version":"2.1.1-1build1"},{"binary_version":"2.1.1-1build1","binary_name":"libdnssec0"},{"binary_name":"libknot1","binary_version":"2.1.1-1build1"},{"binary_version":"2.1.1-1build1","binary_name":"libzscanner0"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39155.json"}},{"package":{"name":"knot","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/knot?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.5.3-3","2.6.0-1","2.6.1-2","2.6.3-1","2.6.4-1","2.6.5-1","2.6.5-3"],"ecosystem_specific":{"binaries":[{"binary_version":"2.6.5-3","binary_name":"knot"},{"binary_name":"knot-dnsutils","binary_version":"2.6.5-3"},{"binary_version":"2.6.5-3","binary_name":"knot-host"},{"binary_name":"libdnssec5","binary_version":"2.6.5-3"},{"binary_name":"libknot7","binary_version":"2.6.5-3"},{"binary_version":"2.6.5-3","binary_name":"libzscanner1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39155.json"}},{"package":{"name":"knot","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/knot?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.7.6-2","2.7.8-1"],"ecosystem_specific":{"binaries":[{"binary_name":"knot","binary_version":"2.7.8-1"},{"binary_name":"knot-dnsutils","binary_version":"2.7.8-1"},{"binary_name":"knot-host","binary_version":"2.7.8-1"},{"binary_name":"libdnssec6","binary_version":"2.7.8-1"},{"binary_version":"2.7.8-1","binary_name":"libknot8"},{"binary_version":"2.7.8-1","binary_name":"libzscanner2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39155.json"}},{"package":{"name":"knot","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/knot?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.5-1ubuntu1","3.1.4-1ubuntu1","3.1.5-1ubuntu1","3.1.6-1ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"knot","binary_version":"3.1.6-1ubuntu1"},{"binary_name":"knot-dnsutils","binary_version":"3.1.6-1ubuntu1"},{"binary_name":"knot-host","binary_version":"3.1.6-1ubuntu1"},{"binary_name":"knot-module-dnstap","binary_version":"3.1.6-1ubuntu1"},{"binary_version":"3.1.6-1ubuntu1","binary_name":"knot-module-geoip"},{"binary_version":"3.1.6-1ubuntu1","binary_name":"libdnssec8"},{"binary_name":"libknot12","binary_version":"3.1.6-1ubuntu1"},{"binary_name":"libzscanner4","binary_version":"3.1.6-1ubuntu1"},{"binary_name":"python3-libknot","binary_version":"3.1.6-1ubuntu1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39155.json"}},{"package":{"name":"knot","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/knot?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.2.9-1","3.3.2-1","3.3.3-1","3.3.3-2","3.3.4-1","3.3.4-1.1build1","3.3.4-1.1build2"],"ecosystem_specific":{"binaries":[{"binary_version":"3.3.4-1.1build2","binary_name":"knot"},{"binary_name":"knot-dnssecutils","binary_version":"3.3.4-1.1build2"},{"binary_name":"knot-dnsutils","binary_version":"3.3.4-1.1build2"},{"binary_name":"knot-exporter","binary_version":"3.3.4-1.1build2"},{"binary_name":"knot-host","binary_version":"3.3.4-1.1build2"},{"binary_version":"3.3.4-1.1build2","binary_name":"knot-module-dnstap"},{"binary_name":"knot-module-geoip","binary_version":"3.3.4-1.1build2"},{"binary_version":"3.3.4-1.1build2","binary_name":"libdnssec9t64"},{"binary_name":"libknot14t64","binary_version":"3.3.4-1.1build2"},{"binary_name":"libzscanner4t64","binary_version":"3.3.4-1.1build2"},{"binary_version":"3.3.4-1.1build2","binary_name":"python3-libknot"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39155.json"}},{"p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