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CVE-2026-123586

Hickory DNS 0.25.0-alpha.3 through 0.25.2 Query Amplification via Cyclic Referrals

Products / packages hickory-dns · hickory-resolver · hickory-recursor

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Severity and exploitation

Not in CISA KEV

KEV coverage does not rule out exploitation.

KEV checked 15/11/2026, 01:40:32 UTC
VulnCheck · CVSS:4.0 · 8.7
Assessment vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
VulnCheck · CVSS:3.1 · 7.5
Assessment vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
The headline uses the highest imported catalog score. Assessments can differ by source and CVSS version.

Severity

high8.7

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Some package fixes recorded

Fix versions are recorded for 1 of 2 mapped packages. Check each release branch and any separate product guidance.

What this means

Hickory DNS versions 0.25.0-alpha.3 through 0.25.2 are affected by a query amplification vulnerability via cyclic referrals. An attacker with control over two zones can cause the recursor to send many upstream queries. This affects the recursive resolver in hickory-resolver and hickory-recursor crates.

Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.

Attack conditions

No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

hickory-dns · VulnCheck

hickory-dns

1 range
VulnCheck version evidence

Package identity

pkg:cargo/hickory-recursorExplore hickory-recursor →

Identity supplied by VulnCheck. Version matching requires compatible range evidence.

Compare with this publisher’s ranges. This does not inspect your installation.

affected

0.25.0-alpha.3 → through 0.25.2

semver versions

unaffected

unknown

Other versions: unaffected

hickory-dns · VulnCheck

hickory-dns

2 ranges
VulnCheck version evidence

Package identity

pkg:cargo/hickory-resolverExplore hickory-resolver →

Identity supplied by VulnCheck. Version matching requires compatible range evidence.

Compare with this publisher’s ranges. This does not inspect your installation.

affected

0 → before 0.26.2

semver versions

unaffected

0.26.2

semver versions

unknown

Other versions: unaffected

Packages

Compare each installed version with the publisher’s affected ranges. Where a fix is recorded, choose the appropriate release branch and test compatibility before upgrading.

hickory-resolver crates.io
Affected range Recorded fix
From 0.26.0-beta.1 before 0.26.2Semantic versions0.26.2

Version evidence: OSV · RUSTSEC-2026-0516

View original version evidence (0 explicit versions)
hickory-recursor crates.io
Affected range Recorded fix
From 0.25.0-alpha.3; no upper bound recordedVersionsNot recorded

Version evidence: OSV · RUSTSEC-2026-0522

View original version evidence (0 explicit versions)

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

Use the recorded fix for your release branch. Review the publisher’s instructions and test compatibility before upgrading.

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher description

Two zones can each delegate to name servers named only inside the other zone, with no glue records (the cyclic sibling case in RFC 9471 section 2.3). Such delegations can never be resolved, but the recursor did not stop when it came back to a zone it was already resolving. It kept sending queries until the per-request limits ran out, and zero TTLs on the referral NS records made this worse.

Someone who controls two such zones can make a recursor send many upstream queries for each client query.

This affects the recursive resolver, which is in hickory-resolver behind the opt-in recursor feature from 0.26.0-beta.1. Earlier releases shipped it as the separate hickory-recursor crate.

From 0.26.2 each client request tracks the zones on its resolution stack and refuses to enter a zone that is already on it.

References

7 sources
hickory-dns/hickory-dns · security/advisories/GHSA-cx5j-p54p-q756
Vendor advisoryVulnCheck
www.vulncheck.com/advisories/hickory-dns-0.25.0-alpha.3-through-0.25.2-query-amplification-via-cyclic-referrals
Security advisoryVulnCheck
crates.io/crates/hickory-resolver
Source reference
rustsec.org/advisories/RUSTSEC-2026-0516.html
Security advisory
hickory-dns/hickory-dns · commit 308dcfd
Patch
crates.io/crates/hickory-recursor
Source reference
View 1 more references
rustsec.org/advisories/RUSTSEC-2026-0522.html
Security advisory

Inside the record

Evidence available

Package identity
Version evidence
Remediation guidance · not supplied
Weakness classification
Additional publishers

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-123586

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-400 ↗

Uncontrolled Resource Consumption

VulnCheck

Related →
Contributing organizations · 2
VulnCheck

Assigning organization

2026-11-08
CISA-ADP

Additional data publisher

2026-11-09

Timeline

All times UTC

  1. Advisory published

    Publication date supplied by the source.

  2. Source updated

    Latest modification date supplied by the source.

  3. Last imported by cve.new

    Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes
  1. CVE · CVE-2026-123586

    Observed 2026-11-09T14:00:49.786Z · upstream updated 2026-11-09T13:54:36.684Z

    Prioritization updated

    before

    []

    after

    [
  {
    "source": "CISA-ADP",
    "type": "SSVC",
    "role": "CISA Coordinator",
    "timestamp": "2026-11-09T13:54:27.883535Z",
    "decisions": [
      {
        "name": "Exploitation",
        "value": "none"
      },
      {
        "name": "Automatable",
        "value": "yes"
      },
      {
        "name": "Technical Impact",
        "value": "partial"
      }
    ]
  }
]

Large field values are marked as truncated previews. Original source snapshots remain retained.

Showing up to 50 most recent observed changes.