{"id":"UBUNTU-CVE-2026-123596","details":"Hickory DNS hickory-proto through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2 contain a DNSSEC validation flaw in the validating recursor's NSEC handler that accepts parent-side ancestor-delegation NSEC records as proof of nonexistence for names below the zone cut. An on-path attacker, rogue parent nameserver, or attacker winning a port and TXID race can deliver one forged NXDOMAIN response built from genuinely signed parent NSEC records, causing authenticated denial of existing child-zone names cached for the negative TTL.","modified":"2026-11-10T02:50:13.454748652Z","published":"2026-11-09T00:00:00Z","upstream":["CVE-2026-123596"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-123596"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-123596"},{"type":"REPORT","url":"https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-3r6v-f3jh-vvqm"},{"type":"REPORT","url":"https://www.vulncheck.com/advisories/hickory-dns-through-0.26.0-alpha.1-dnssec-validation-bypass-via-ancestor-delegation-nsec"}],"affected":[{"package":{"name":"rust-hickory-proto","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/rust-hickory-proto?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.24.0-1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.24.0-1","binary_name":"librust-hickory-proto-dev"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-123596.json"}},{"package":{"name":"rust-hickory-net","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/rust-hickory-net?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.26.1-1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.26.1-1","binary_name":"librust-hickory-net-dev"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-123596.json"}},{"package":{"name":"rust-hickory-proto","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/rust-hickory-proto?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.24.4-6","0.26.1-1"],"ecosystem_specific":{"binaries":[{"binary_name":"librust-hickory-proto-dev","binary_version":"0.26.1-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-123596.json"}},{"package":{"name":"rust-hickory-proto","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/rust-hickory-proto?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.24.4-4.1","0.24.4-6"],"ecosystem_specific":{"binaries":[{"binary_version":"0.24.4-6","binary_name":"librust-hickory-proto-dev"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-123596.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"},{"type":"Ubuntu","score":"medium"}]}