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HIGH severity

CVE-2026-123596 — Hickory-Dns

HIGH

CVE-2026-123596 is a high-severity (CVSS 8.8) CWE-345 vulnerability in hickory-dns hickory-dns. A fix is available — see the affected versions and patch details below.

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…

Published
Updated
Affected
2 products
Patched
See advisory
Exploits
None indexed
Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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.

Affected Products

2 products · 2 configurations
Application
hickory-dnshickory-dns
≤ 0.26.0-alpha.1
1 version
0
Application
hickory-dnshickory-dns
< 0.26.2
1 version
0.26.0-beta.1

Detection & mitigation playbook

Vendor / appliance

  1. Detect

    Inventory every hickory-dns hickory-dns deployment and check each version against the affected-products list above.

  2. Fix

    Apply the hickory-dns hickory-dns security patch or hotfix for CVE-2026-123596 on the affected version, following the vendor advisory for your exact build.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

Frequently Asked Questions

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.
O3 Security · Runtime Protection

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