{"schemaVersion":3,"id":"CVE-2026-5947","aliases":["ALPINE-CVE-2026-5947","UBUNTU-CVE-2026-5947","DEBIAN-CVE-2026-5947"],"status":"published","duplicateOf":null,"title":null,"description":"Undefined behavior may result due to a race condition leading to a use-after-free violation.  If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature.  If, during that validation, the \"recursive-clients\" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message.\nThis issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1.\nBIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.","dates":{"published":"2026-05-20T13:10:11.873Z","modified":"2026-09-01T12:05:00.589Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":7.5,"severity":"high","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","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","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Alpine","score":5.9,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","exploitability":5.6,"impact":6,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · 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Debian","score":5.9,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","exploitability":5.6,"impact":6,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":5.9,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00799,"percentile":0.55786,"severity":"low","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":-0.588,"baselineDate":"2026-09-19T00:00:00.000Z","baselineScore":0.01387},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00799,"percentile":0.55786}],"last30":[{"date":"2026-09-19T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.01387,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00799,"percentile":null},{"date":"2026-10-16T00:00:00.00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Execution using Shared Resource with Improper Synchronization ('Race Condition')","description":"The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.","type":"weakness","status":"Draft","abstraction":"Class","likelihoodOfExploit":"Medium","url":"https://cwe.mitre.org/data/definitions/362.html"},{"id":"CWE-416","name":"Use After Free","description":"The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory \"belongs\" to the code that operates on the new pointer.","type":"weakness","status":"Stable","abstraction":"Variant","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/416.html"},{"id":"CWE-367","name":"Time-of-check Time-of-use (TOCTOU) Race Condition","description":"The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.","type":"weakness","status":"Incomplete","abstraction":"Base","likelihoodOfExploit":"Medium","url":"https://cwe.mitre.org/data/definitions/367.html"}],"affected":[{"vendor":"alpine","product":"bind","name":"bind","label":"bind","ecosystem":"Alpine Linux","cpePart":null,"purl":"pkg:apk/alpine/bind","purlType":"apk","versions":[{"text":"≥ 9.20.0, < 9.18.49-r0","noFixRecorded":false,"fixedIn":null},{"text":"≥ 9.20.0, < 9.20.23-r0","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 9.20.0, < 9.18.49-r0 | ≥ 9.20.0, < 9.20.23-r0","eol":null,"hubHref":null},{"vendor":"debian","product":"bind9","name":"bind9","label":"bind9","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/bind9","purlType":"deb","versions":[{"text":"< 1:9.20.23-1~deb13u1","noFixRecorded":false,"fixedIn":null},{"text":"< 1:9.20.23-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1:9.20.23-1~deb13u1 | < 1:9.20.23-1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"bind9","name":"bind9","label":"bind9","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/bind9","purlType":"deb","versions":[{"text":"< 1:9.20.11-1ubuntu2.4","noFixRecorded":false,"fixedIn":null},{"text":"< 1:9.20.18-1ubuntu2.1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1:9.20.11-1ubuntu2.4 | < 1:9.20.18-1ubuntu2.1","eol":null,"hubHref":null},{"vendor":"isc","product":"bind","name":"BIND","label":"bind","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 9.20.0, < 9.20.23","noFixRecorded":false,"fixedIn":null},{"text":"≥ 9.21.0, < 9.21.22","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 9.20.0, < 9.20.23 | ≥ 9.21.0, < 9.21.22","eol":null,"hubHref":"/vendor/isc/bind"},{"vendor":"isc","product":"bind 9","name":"BIND 9","label":"bind 9","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 9.20.0, ≤ 9.20.22","noFixRecorded":false,"fixedIn":null},{"text":"≥ 9.21.0, ≤ 9.21.21","noFixRecorded":false,"fixedIn":null},{"text":"≥ 9.20.9-S1, ≤ 9.20.22-S1","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 9.20.0, ≤ 9.20.22 | ≥ 9.21.0, ≤ 9.21.21 | ≥ 9.20.9-S1, ≤ 9.20.22-S1","eol":{"isEol":null,"eolDate":null,"matchMethod":"name_exact","cycle":null,"product":{"name":"bind-9","label":"BIND 9","category":"server-app"}},"hubHref":"/vendor/isc/bind_9"}],"affectedCount":5,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://kb.isc.org/docs/cve-2026-5947","label":"kb.isc.org/docs/cve-2026-5947","hostname":"kb.isc.org","tags":["Vendor Advisory","REPORT"]},{"url":"https://downloads.isc.org/isc/bind9/9.20.23","label":"downloads.isc.org/isc/bind9/9.20.23","hostname":"downloads.isc.org","tags":["Patch"]},{"url":"https://downloads.isc.org/isc/bind9/9.21.22","label":"downloads.isc.org/isc/bind9/9.21.22","hostname":"downloads.isc.org","tags":["Patch"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-5947","label":"access.redhat.com/security/cve/CVE-2026-5947","hostname":"access.redhat.com","tags":["VDB Entry","X Refsource REDHAT"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2479772","label":"bugzilla.redhat.com/show_bug.cgi?id=2479772","hostname":"bugzilla.redhat.com","tags":["Issue Tracking","X Refsource REDHAT"]},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5947.json","label":"security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5947.json","hostname":"security.access.redhat.com","tags":["X Sadp Csaf Vex"]},{"url":"https://access.redhat.com/errata/RHSA-2026:7412","label":"access.redhat.com/errata/RHSA-2026:7412","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://security.alpinelinux.org/vuln/CVE-2026-5947","label":"security.alpinelinux.org/vuln/CVE-2026-5947","hostname":"security.alpinelinux.org","tags":["Advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-5947","label":"ubuntu.com/security/CVE-2026-5947","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-5947","label":"www.cve.org/CVERecord?id=CVE-2026-5947","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://ubuntu.com/security/notices/USN-8293-1","label":"ubuntu.com/security/notices/USN-8293-1","hostname":"ubuntu.com","tags":["Advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-5947","label":"security-tracker.debian.org/tracker/CVE-2026-5947","hostname":"security-tracker.debian.org","tags":["Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5947","label":"nvd.nist.gov/vuln/detail/CVE-2026-5947","hostname":"nvd.nist.gov","tags":["Oval","Advisory"]}],"lineage":{"upstream":[],"downstream":["MGASA-2026-0163","OPENSUSE-SU-2026:10874-1","OPENSUSE-SU-2026:21123-1","RHSA-2026:7412","SUSE-SU-2026:22198-1","SUSE-SU-2026:2673-1"],"duplicates":[],"related":["OPENSUSE-SU-2026:10874-1","OPENSUSE-SU-2026:21123-1","SUSE-SU-2026:22198-1","SUSE-SU-2026:2673-1","USN-8293-1"]},"timeline":[{"kind":"published","date":"2026-05-20T13:10:11.873Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-09-01T12:05:00.589Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":30,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-20T11:17:02.114Z","stale":false,"partial":false}}