{"id":"UBUNTU-CVE-2026-5947","details":"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. This 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. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.","modified":"2026-05-29T10:45:35.821426011Z","published":"2026-05-20T00:00:00Z","related":["USN-8293-1"],"upstream":["CVE-2026-5947"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-5947"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-5947"},{"type":"REPORT","url":"https://kb.isc.org/docs/cve-2026-5947"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8293-1"}],"affected":[{"package":{"name":"bind9-libs","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/bind9-libs?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:9.11.16+dfsg-3~build1","1:9.11.16+dfsg-3~ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"libbind9-161","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libdns-export1109","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libdns1109","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libirs-export161","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libirs161","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libisc-export1105","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libisc1105","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libisccc-export161","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libisccc161","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libisccfg-export163","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"libisccfg163","binary_version":"1:9.11.16+dfsg-3~ubuntu1"},{"binary_name":"liblwres161","binary_version":"1:9.11.16+dfsg-3~ubuntu1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-5947.json"}},{"package":{"name":"bind9-libs","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/bind9-libs?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:9.11.19+dfsg-2.1ubuntu1","1:9.11.19+dfsg-2.1ubuntu2","1:9.11.19+dfsg-2.1ubuntu3"],"ecosystem_specific":{"binaries":[{"binary_name":"libbind9-161","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libdns-export1110","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libdns1110","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libirs-export161","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libirs161","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libisc-export1105","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libisc1105","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libisccc-export161","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libisccc161","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libisccfg-export163","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"libisccfg163","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"},{"binary_name":"liblwres161","binary_version":"1:9.11.19+dfsg-2.1ubuntu3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-5947.json"}},{"package":{"name":"bind9","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/bind9?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:9.20.11-1ubuntu2.4"}]}],"versions":["1:9.20.4-3ubuntu1","1:9.20.4-3ubuntu2","1:9.20.4-3ubuntu3","1:9.20.9-2ubuntu1","1:9.20.10-1ubuntu1","1:9.20.11-1ubuntu1","1:9.20.11-1ubuntu2","1:9.20.11-1ubuntu2.1","1:9.20.11-1ubuntu2.2"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"bind9","binary_version":"1:9.20.11-1ubuntu2.4"},{"binary_name":"bind9-dnsutils","binary_version":"1:9.20.11-1ubuntu2.4"},{"binary_name":"bind9-host","binary_version":"1:9.20.11-1ubuntu2.4"},{"binary_name":"bind9-libs","binary_version":"1:9.20.11-1ubuntu2.4"},{"binary_name":"bind9-utils","binary_version":"1:9.20.11-1ubuntu2.4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-5947.json"}},{"package":{"name":"bind9","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/bind9?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:9.20.18-1ubuntu2.1"}]}],"versions":["1:9.20.11-1ubuntu2","1:9.20.11-1ubuntu3","1:9.20.18-1ubuntu1","1:9.20.18-1ubuntu2"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"bind9","binary_version":"1:9.20.18-1ubuntu2.1"},{"binary_name":"bind9-dnsutils","binary_version":"1:9.20.18-1ubuntu2.1"},{"binary_name":"bind9-host","binary_version":"1:9.20.18-1ubuntu2.1"},{"binary_name":"bind9-libs","binary_version":"1:9.20.18-1ubuntu2.1"},{"binary_name":"bind9-utils","binary_version":"1:9.20.18-1ubuntu2.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-5947.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}