{"id":"CVE-2026-123603","title":"Hickory DNS Missing IPv4-Mapped IPv6 Canonicalization Access Control Bypass","summary":"hickory-proto and hickory-resolver 0.26.0 before 0.26.2, hickory-server 0.25.0-alpha.1 before 0.26.2, and hickory-recursor 0.25.0-alpha.3 through 0.26.0-alpha.1 fail to canonicalize IPv4-mapped IPv6 addresses when checking deny_answers, …","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","cvssSource":"cna","cwe":["CWE-284"],"vendor":"hickory-dns","product":"hickory-dns","affected":["hickory-dns >= 0.25.0-alpha.3 <= 0.26.0-alpha.1","hickory-dns >= 0.26.0 < 0.26.2","hickory-dns >= 0.26.0 < 0.26.2","hickory-dns >= 0.25.0-alpha.1 < 0.26.2"],"published":"2026-11-08","updated":"2026-11-08","sourceUpdated":"2026-11-08T01:38:30.679Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-123603","references":[{"url":"https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-4jwp-xjwm-333g","label":"GitHub Security Advisory (GHSA-4jwp-xjwm-333g)"},{"url":"https://www.vulncheck.com/advisories/hickory-dns-missing-ipv4-mapped-ipv6-canonicalization-access-control-bypass","label":"VulnCheck Advisory: Hickory DNS Missing IPv4-Mapped IPv6 Canonicalization Access Control Bypass"}],"tags":["cve.org"],"ingestedAt":"2026-11-08T02:43:18.641Z","slug":"CVE-2026-123603","body":"## Overview\n\nhickory-proto and hickory-resolver 0.26.0 before 0.26.2, hickory-server 0.25.0-alpha.1 before 0.26.2, and hickory-recursor 0.25.0-alpha.3 through 0.26.0-alpha.1 fail to canonicalize IPv4-mapped IPv6 addresses when checking deny_answers, deny_server, or AccessControlSet rules. Attackers can use IPv4-mapped addresses to evade answer filtering, trigger queries to denied nameservers, or reach hickory-server library deployments on dual-stack IPv6 sockets from denied clients.\n\n## Affected\n\n- `hickory-dns >= 0.25.0-alpha.3 <= 0.26.0-alpha.1`\n- `hickory-dns >= 0.26.0 < 0.26.2`\n- `hickory-dns >= 0.26.0 < 0.26.2`\n- `hickory-dns >= 0.25.0-alpha.1 < 0.26.2`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}