{"api_version":"1","generated_at":"2026-07-24T21:12:24+00:00","cve":"CVE-2026-11721","urls":{"html":"https://cve.report/CVE-2026-11721","api":"https://cve.report/api/cve/CVE-2026-11721.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-11721","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-11721"},"summary":{"title":"Cache poisoning possible with label count discrepancy, RRSIG, and wildcards","description":"It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker's zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default).\nThis issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.","state":"PUBLISHED","assigner":"isc","published_at":"2026-07-22 15:16:51","updated_at":"2026-07-22 20:33:11"},"problem_types":["CWE-1284","CWE-1284 CWE-1284 Improper Validation of Specified Quantity in Input"],"metrics":[{"version":"3.1","source":"security-officer@isc.org","type":"Secondary","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"NONE"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","data":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","version":"3.1"}}],"references":[{"url":"https://kb.isc.org/docs/cve-2026-11721","name":"https://kb.isc.org/docs/cve-2026-11721","refsource":"security-officer@isc.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://downloads.isc.org/isc/bind9/9.21.24","name":"https://downloads.isc.org/isc/bind9/9.21.24","refsource":"security-officer@isc.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://downloads.isc.org/isc/bind9/9.20.26","name":"https://downloads.isc.org/isc/bind9/9.20.26","refsource":"security-officer@isc.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-11721","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-11721","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"ISC","product":"BIND 9","version":"affected 9.11.0 9.18.50 custom","platforms":[]},{"source":"CNA","vendor":"ISC","product":"BIND 9","version":"affected 9.20.0 9.20.24 custom","platforms":[]},{"source":"CNA","vendor":"ISC","product":"BIND 9","version":"affected 9.21.0 9.21.23 custom","platforms":[]},{"source":"CNA","vendor":"ISC","product":"BIND 9","version":"affected 9.11.3-S1 9.18.50-S1 custom","platforms":[]},{"source":"CNA","vendor":"ISC","product":"BIND 9","version":"affected 9.20.9-S1 9.20.24-S1 custom","platforms":[]}],"timeline":[],"solutions":[{"source":"CNA","title":"","value":"Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.26, 9.21.24, or 9.20.26-S1.","time":"","lang":"en"}],"workarounds":[{"source":"CNA","title":"","value":"No workarounds known.","time":"","lang":"en"}],"exploits":[{"source":"CNA","title":"","value":"We are not aware of any active exploits.","time":"","lang":"en"}],"credits":[{"source":"CNA","value":"ISC would like to thank Qifan Zhang of Palo Alto Networks for bringing this vulnerability to our attention.","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"other":{"content":{"id":"CVE-2026-11721","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","timestamp":"2026-07-22T18:52:35.390125Z","version":"2.0.3"},"type":"ssvc"}}],"providerMetadata":{"dateUpdated":"2026-07-22T18:52:46.888Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"defaultStatus":"unaffected","product":"BIND 9","vendor":"ISC","versions":[{"lessThanOrEqual":"9.18.50","status":"affected","version":"9.11.0","versionType":"custom"},{"lessThanOrEqual":"9.20.24","status":"affected","version":"9.20.0","versionType":"custom"},{"lessThanOrEqual":"9.21.23","status":"affected","version":"9.21.0","versionType":"custom"},{"lessThanOrEqual":"9.18.50-S1","status":"affected","version":"9.11.3-S1","versionType":"custom"},{"lessThanOrEqual":"9.20.24-S1","status":"affected","version":"9.20.9-S1","versionType":"custom"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionEndIncluding":"9.18.50","versionStartIncluding":"9.11.0","vulnerable":true},{"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionEndIncluding":"9.20.24","versionStartIncluding":"9.20.0","vulnerable":true},{"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionEndIncluding":"9.21.23","versionStartIncluding":"9.21.0","vulnerable":true},{"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionEndIncluding":"9.18.50-S1","versionStartIncluding":"9.11.3-S1","vulnerable":true},{"criteria":"cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*","versionEndIncluding":"9.20.24-S1","versionStartIncluding":"9.20.9-S1","vulnerable":true}],"operator":"OR"}]}],"credits":[{"lang":"en","value":"ISC would like to thank Qifan Zhang of Palo Alto Networks for bringing this vulnerability to our attention."}],"datePublic":"2026-07-22T00:00:00.000Z","descriptions":[{"lang":"en","value":"It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker's zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default).\nThis issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1."}],"exploits":[{"lang":"en","value":"We are not aware of any active exploits."}],"impacts":[{"descriptions":[{"lang":"en","value":"Potential cache poisoning."}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1284","description":"CWE-1284 Improper Validation of Specified Quantity in Input","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-07-22T14:13:08.748Z","orgId":"404fd4d2-a609-4245-b543-2c944a302a22","shortName":"isc"},"references":[{"name":"CVE-2026-11721","tags":["vendor-advisory"],"url":"https://kb.isc.org/docs/cve-2026-11721"},{"tags":["patch"],"url":"https://downloads.isc.org/isc/bind9/9.20.26"},{"tags":["patch"],"url":"https://downloads.isc.org/isc/bind9/9.21.24"}],"solutions":[{"lang":"en","value":"Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.26, 9.21.24, or 9.20.26-S1."}],"source":{"discovery":"EXTERNAL"},"title":"Cache poisoning possible with label count discrepancy, RRSIG, and wildcards","workarounds":[{"lang":"en","value":"No workarounds known."}],"x_generator":{"engine":"cvelib 1.8.0"}}},"cveMetadata":{"assignerOrgId":"404fd4d2-a609-4245-b543-2c944a302a22","assignerShortName":"isc","cveId":"CVE-2026-11721","datePublished":"2026-07-22T14:13:08.748Z","dateReserved":"2026-06-09T01:19:47.697Z","dateUpdated":"2026-07-22T18:52:46.888Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-22 15:16:51","lastModifiedDate":"2026-07-22 20:33:11","problem_types":["CWE-1284","CWE-1284 CWE-1284 Improper Validation of Specified Quantity in Input"],"metrics":{"cvssMetricV31":[{"source":"security-officer@isc.org","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"NONE"},"exploitabilityScore":3.9,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-07-22T18:52:35.390125Z","id":"CVE-2026-11721","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"11721","Ordinal":"1","Title":"Cache poisoning possible with label count discrepancy, RRSIG, an","CVE":"CVE-2026-11721","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"11721","Ordinal":"1","NoteData":"It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker's zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default).\nThis issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.","Type":"Description","Title":"Cache poisoning possible with label count discrepancy, RRSIG, an"}]}}}