Hickory DNS through 0.26.0-alpha.1 DNSSEC Validation Bypass via Ancestor-Delegation NSEC
Affects hickory-proto up to 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2 when the validating recursor is in use. Fixed in 0.26.2.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 0.26.2
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Hickory DNS hickory-proto up to 0.26.0-alpha.1, or hickory-net 0.26.0-beta.1 before 0.26.2 (affected versions listed as 0.26.0-beta.1 to 0.26.1) The validating recursor is in use, with its NSEC handler processing parent-side delegation NSEC records
- Published
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 17/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure8/25Specific setups only, reachable over the network
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.7/10CVSS 8.7
- No patch0/5No signal
What would change the score
- Would score about 67 if added to CISA KEV
- Would score about 62 if CISA's SSVC rates exploitation active
- Would score about 24 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
Hickory DNS hickory-proto up to 0.26.0-alpha.1, or hickory-net 0.26.0-beta.1 before 0.26.2 (affected versions listed as 0.26.0-beta.1 to 0.26.1) The validating recursor is in use, with its NSEC handler processing parent-side delegation NSEC recordsUpgrade to a fixed version: 0.26.2.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- hickory-dns hickory-dns
through 0.26.0-alpha.1
- hickory-dns hickory-dns
From 0.26.0-beta.1 · fixed in 0.26.2
Evidence 2
- Advisory
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-123596
Is CVE-2026-123596 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
The validating recursor's NSEC handler does not distinguish parent-side delegation NSEC records. As a result, it can return NXDOMAIN with AD=1 for names that exist in a child zone, and that negative result is cached for the negative TTL.Source: vulncheck.com, github.com
Which versions are affected by CVE-2026-123596?
hickory-dns: through 0.26.0-alpha.1. hickory-dns: from 0.26.0-beta.1 before 0.26.2.Source: cve.now feed data
Am I affected, and how do I check?
Affected are hickory-proto up to and including 0.26.0-alpha.1, and hickory-net from 0.26.0-beta.1 before 0.26.2 (listed as 0.26.0-beta.1 to 0.26.1). The issue applies when the validating recursor is in use. To check, look at the hickory-proto or hickory-net version in your build and whether the validating recursor is enabled in your configuration.Source: vulncheck.com, github.com
How do I fix CVE-2026-123596?
Upgrade to hickory-net 0.26.2 or later. This is the fixed version listed in the advisory.Source: vulncheck.com, github.com