{"id":"UBUNTU-CVE-2026-5950","details":"An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions. This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.","modified":"2026-07-31T01:59:55.319799223Z","published":"2026-05-20T00:00:00Z","related":["USN-8293-1"],"upstream":["CVE-2026-5950"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-5950"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-5950"},{"type":"REPORT","url":"https://kb.isc.org/docs/cve-2026-5950"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8293-1"}],"affected":[{"package":{"name":"isc-dhcp","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/isc-dhcp?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.3.5-3ubuntu2","4.3.5-3ubuntu3","4.3.5-3ubuntu4","4.3.5-3ubuntu5","4.3.5-3ubuntu6","4.3.5-3ubuntu7","4.3.5-3ubuntu7.1","4.3.5-3ubuntu7.2","4.3.5-3ubuntu7.3","4.3.5-3ubuntu7.4"],"ecosystem_specific":{"binaries":[{"binary_version":"4.3.5-3ubuntu7.4","binary_name":"isc-dhcp-client"},{"binary_name":"isc-dhcp-client-ddns","binary_version":"4.3.5-3ubuntu7.4"},{"binary_name":"isc-dhcp-common","binary_version":"4.3.5-3ubuntu7.4"},{"binary_version":"4.3.5-3ubuntu7.4","binary_name":"isc-dhcp-relay"},{"binary_version":"4.3.5-3ubuntu7.4","binary_name":"isc-dhcp-server"},{"binary_name":"isc-dhcp-server-ldap","binary_version":"4.3.5-3ubuntu7.4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-5950.json"}},{"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_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_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-2026-5950.json"}},{"package":{"name":"bind9","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/bind9?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:9.18.39-0ubuntu0.22.04.4"}]}],"versions":["1:9.16.15-1ubuntu1","1:9.16.15-1ubuntu2","1:9.16.15-1ubuntu3","1:9.18.0-2ubuntu1","1:9.18.0-2ubuntu2","1:9.18.0-2ubuntu3","1:9.18.1-1ubuntu1","1:9.18.1-1ubuntu1.1","1:9.18.1-1ubuntu1.2","1:9.18.1-1ubuntu1.3","1:9.18.12-0ubuntu0.22.04.1","1:9.18.12-0ubuntu0.22.04.2","1:9.18.12-0ubuntu0.22.04.3","1:9.18.18-0ubuntu0.22.04.1","1:9.18.18-0ubuntu0.22.04.2","1:9.18.24-0ubuntu0.22.04.1","1:9.18.28-0ubuntu0.22.04.1","1:9.18.30-0ubuntu0.22.04.1","1:9.18.30-0ubuntu0.22.04.2","1:9.18.39-0ubuntu0.22.04.1","1:9.18.39-0ubuntu0.22.04.2","1:9.18.39-0ubuntu0.22.04.3"],"ecosystem_specific":{"availability":"No 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