Hickory-DNS Recursor 0.25.0-alpha.3 through 0.25.2 Glueless-NS Referral Amplification
Affects hickory-recursor 0.25.0-alpha.3 through 0.25.2, and hickory-resolver 0.26.0-alpha.1 before 0.26.2 when the opt-in recursor feature is enabled. 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. Affects hickory-recursor 0.25.0-alpha.3 through 0.25.2. Affects hickory-resolver 0.26.0-alpha.1 before 0.26.2, where the recursor is behind the opt-in recursor feature. The recursor receives a referral whose NS targets are out-of-bailiwick and have no glue.
- 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? →
- 21/100 · 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
The hickory-dns recursor in hickory-recursor 0.25.0-alpha.3 through 0.25.2 and hickory-resolver 0.26.0-alpha.1 before 0.26.2 iterates every out-of-bailiwick NS target lacking glue in a referral without any per-query work budget. Remote attackers can serve such referrals to force A and AAAA lookups per target, amplifying traffic against remote servers or exhausting recursor resources.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure12/25Specific setups only, reachable over the network without a login
- 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 71 if added to CISA KEV
- Would score about 66 if CISA's SSVC rates exploitation active
What to do
Check whether your setup matches what the bug needs.
Affects hickory-recursor 0.25.0-alpha.3 through 0.25.2. Affects hickory-resolver 0.26.0-alpha.1 before 0.26.2, where the recursor is behind the opt-in recursor feature. The recursor receives a referral whose NS targets are out-of-bailiwick and have no glue.Upgrade to a fixed version: 0.26.2.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- hickory-dns hickory-dns
From 0.25.0-alpha.3 · through 0.25.2
- hickory-dns hickory-dns
From 0.26.0-alpha.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-2026-123606
Is CVE-2026-123606 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?
When the Hickory DNS recursor receives a referral whose NS targets are out-of-bailiwick and have no glue, it forces A and AAAA lookups for each NS target. This can amplify traffic against remote servers or exhaust the recursor's resources.Source: vulncheck.com, github.com
Which versions are affected by CVE-2026-123606?
hickory-dns: from 0.25.0-alpha.3 through 0.25.2. hickory-dns: from 0.26.0-alpha.1 before 0.26.2.Source: cve.now feed data
Am I affected, and how do I check?
The listed ranges are hickory-recursor 0.25.0-alpha.3 through 0.25.2, and hickory-resolver 0.26.0-alpha.1 before 0.26.2 where the opt-in recursor feature is in use. To check, look at the hickory-dns version in the build or Cargo.lock and whether the recursor feature is enabled.Source: vulncheck.com, github.com
How do I fix CVE-2026-123606?
Upgrade hickory-resolver to 0.26.2, the only fixed version listed in the facts. The facts do not give a fixed release for the 0.25 line.Source: vulncheck.com, github.com