CVE-2026-123603
Hickory DNS Missing IPv4-Mapped IPv6 Canonicalization Access Control Bypass
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.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| hickory-dns hickory-dns hickory-recursor
cargo |
≥ 0.25.0-alpha.3; ≤ 0.26.0-alpha.1 (affected, semver)
Other versions: unaffected |
CNA: VulnCheck |
| hickory-dns hickory-dns hickory-resolver
cargo |
≥ 0.26.0; < 0.26.2 (affected, semver) 0.26.2 (unaffected, semver) Other versions: unaffected |
CNA: VulnCheck |
| hickory-dns hickory-dns hickory-proto
cargo |
≥ 0.26.0; < 0.26.2 (affected, semver) 0.26.2 (unaffected, semver) Other versions: unaffected |
CNA: VulnCheck |
| hickory-dns hickory-dns hickory-server
cargo |
≥ 0.25.0-alpha.1; < 0.26.2 (affected, semver) 0.26.2 (unaffected, semver) Other versions: unaffected |
CNA: VulnCheck |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 6.9 medium |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N | CNA: VulnCheck |
| 3.1 / 6.5 medium |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N | CNA: VulnCheck |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-4jwp-xjwm-333gCNA: VulnCheck · vendor-advisory
- https://www.vulncheck.com/advisories/hickory-dns-missing-ipv4-mapped-ipv6-canonicalization-access-control-bypassCNA: VulnCheck · third-party-advisory
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