---
id: "CVE-2026-123596"
page: "https://infrastack.ai/live/CVE-2026-123596"
kind: "vulnerability"
aliases: ["CVE-2026-123596"]
title: "Hickory DNS: forged NXDOMAIN denies existing DNSSEC child-zone names"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["dns-resolver", "dnssec", "hickory-dns", "package", "rust"]
not_affected_if: ["dnssec-validation-off", "no-validating-recursor"]
published_at: "2026-11-08T02:16:54+00:00"
first_seen_at: "2026-11-08T02:21:13+00:00"
updated_at: "2026-11-08T02:22:38+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123596", "first_seen_at": "2026-11-08T02:21:13+00:00"}]
exploit_sources: []
---

# Hickory DNS: forged NXDOMAIN denies existing DNSSEC child-zone names

Link for people: https://infrastack.ai/live/CVE-2026-123596 (this .md is for agents)

Hickory DNS's validating recursor accepts parent-side NSEC records as proof that names below a zone cut do not exist. An on-path attacker or rogue parent nameserver can send one forged NXDOMAIN, so existing child-zone names are denied and cached for the negative TTL.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the `hickory-proto` and `hickory-net` versions in your Cargo.lock or dependency tree; affected if `hickory-proto` is through `0.26.0-alpha.1` or `hickory-net` is `0.26.0-beta.1`.
- Check whether your service runs the Hickory validating recursor (resolver) rather than only an authoritative server or a client library.

## Fix

- `hickory-net` and `hickory-proto`: move to `0.26.2` or later.

## Timeline

- 2026-11-08T02:21:13+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123596

## Documents

- [advisory] Vendor advisory: github.com https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-3r6v-f3jh-vvqm
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/hickory-dns-through-0.26.0-alpha.1-dnssec-validation-bypass-via-ancestor-delegation-nsec

## From the sources

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.

---

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