{"id":"CVE-2026-5947","title":"Undefined behavior may result due to a race condition leading to a use-after-free violation","summary":"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 \"recur…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-362","CWE-416","CWE-367"],"vendor":"isc","product":"bind","affected":["bind >= 9.20.0, < 9.20.23","bind >= 9.21.0, < 9.21.22"],"patched":["bind 9.21.22"],"published":"2026-05-20","updated":"2026-07-23","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-5947","references":[{"url":"https://downloads.isc.org/isc/bind9/9.20.23","label":"security-officer@isc.org"},{"url":"https://downloads.isc.org/isc/bind9/9.21.22","label":"security-officer@isc.org"},{"url":"https://kb.isc.org/docs/cve-2026-5947","label":"security-officer@isc.org"},{"url":"https://access.redhat.com/errata/RHSA-2026:7412","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/security/cve/CVE-2026-5947","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2479772","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5947.json","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}],"tags":["nvd"],"epss":0.01387,"epssPercentile":0.70617,"ingestedAt":"2026-07-23T12:17:54.909Z","slug":"CVE-2026-5947","body":"## Overview\n\nUndefined 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.\n\n## Affected\n\n- `bind >= 9.20.0, < 9.20.23`\n- `bind >= 9.21.0, < 9.21.22`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `bind 9.21.22`","depth":"twilight","depthScore":42,"depthScoreParts":{"impact":41.3,"likelihood":0.3,"exploitation":0,"ransomware":0},"changes":[]}