Hickory DNS through 0.26.0-alpha.1 DNSSEC Validation Bypass via Ancestor-Delegation NSEC3
Affects hickory-proto 0.25 through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2, when the validating recursor's NSEC3 handler is used. 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. Uses the validating recursor's NSEC3 handler (hickory-proto 0.25 through 0.26.0-alpha.1, or hickory-net 0.26.0-beta.1 before 0.26.2). Affected release range: hickory-proto 0.25 through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2.
- 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 0.25 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 NSEC3 handler, which matches the closest encloser by hash alone without checking the type bitmap and so accepts parent-side ancestor-delegation NSEC3 records as proof of nonexistence. An attacker who delivers one response built from genuinely signed parent NSEC3 records can cause NXDOMAIN or NODATA to be cached with AD=1, denying resolution of existing names at and below the zone cut.
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.
Uses the validating recursor's NSEC3 handler (hickory-proto 0.25 through 0.26.0-alpha.1, or hickory-net 0.26.0-beta.1 before 0.26.2). Affected release range: hickory-proto 0.25 through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2.Upgrade to a fixed version: 0.26.2.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- hickory-dns hickory-dns
From 0.25 · 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-2026-123595
Is CVE-2026-123595 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 NSEC3 handler does not implement the check needed for ancestor-delegation NSEC3 records. As a result, the resolver can cache a forged NXDOMAIN or NODATA response marked AD=1, which denies resolution of names that legitimately exist at and below the zone cut.Source: github.com, vulncheck.com
Which versions are affected by CVE-2026-123595?
hickory-dns: from 0.25 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?
The affected releases are hickory-proto 0.25 through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2. To check a project, look up the installed hickory-proto or hickory-net version in its dependency lockfile and confirm whether it uses the validating recursor.Source: github.com, vulncheck.com
How do I fix CVE-2026-123595?
Upgrade to hickory-net 0.26.2, which is the fixed release. Projects that use hickory-proto should move to the release that contains the fix as listed in the advisory.Source: github.com, vulncheck.com