Vulnerability in Hickory-Dns
CVE-2026-123603
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, 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.
Published .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/hickory-dns/hickory-dns/security/advisories/GHSA-4jwp-xjwm-333g (vendor-advisory)
- www.vulncheck.com/advisories/hickory-dns-missing-ipv4-mapped-ipv6-canonicalizat… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-123603?
- CVE-2026-123603 is a medium-severity vulnerability in Hickory-Dns, classified under Improper Access Control. CVSS score: 6.5/10. Published 2026-11-08.
- How severe is CVE-2026-123603?
- Medium severity. CVSS v3 base score is 6.5 out of 10.