{"id":"CVE-2026-123596","published":"2026-11-08T02:16:54.020","lastModified":"2026-11-10T22:15:59.797","description":"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.","cvssScore":8.8,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cwes":["CWE-345"],"vendors":[],"products":[],"references":[{"url":"https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-3r6v-f3jh-vvqm","tags":[]},{"url":"https://www.vulncheck.com/advisories/hickory-dns-through-0.26.0-alpha.1-dnssec-validation-bypass-via-ancestor-delegation-nsec","tags":[]}],"exploitRefs":[{"url":"https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-3r6v-f3jh-vvqm","tags":[]}],"hasPoc":true,"ai":{"summary":"A DNSSEC validation flaw in Hickory DNS's NSEC handler incorrectly accepts parent-zone ancestor-delegation NSEC records as proof of nonexistence for names below a zone cut, enabling attackers to forge authenticated NXDOMAIN responses. This allows denial of service for legitimate child-zone names by caching false negative responses for the negative TTL.","exploitability":"Exploitation requires on-path positioning, control of a rogue parent nameserver, or winning a port/TXID race condition; low privilege access (PR:L) is required but not sufficient alone.","blast_radius":"Successful exploitation causes authenticated denial of existing child-zone names across affected resolvers, potentially disrupting resolution for multiple downstream clients relying on the compromised cache.","remediation":"Upgrade to hickory-proto and hickory-net version 0.26.2 or later, as this is the exact fixed version specified in the CVE description.","detection":"No reliable host or network indicator is derivable from the published description.","tags":["dnssec","nsec","dos","cache-poisoning","recursor"],"model":"garnet-coder","analyzedAt":"2026-11-08T09:54:05.362Z"}}