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CVE-2026-123604

hickory-resolver: Unbounded TC-retry loop in `NameServerPool::try_send` (resource-exhaustion DoS)

Products / packages hickory-dns · hickory-resolver

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Severity and exploitation

Not in CISA KEVSource: HIGH

KEV coverage does not rule out exploitation.

KEV checked 15/11/2026, 01:40:32 UTC
OSV · 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: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

Package fixes recorded

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

What this means

The hickory-resolver name server pool implementation has an unbounded TC-retry loop vulnerability in versions before 0.26.2, allowing an authoritative server to cause a resource-exhaustion denial-of-service by setting the TC header bit. An attacker with access to the name server pool can exploit this weakness. The impact is a potential denial-of-service.

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

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

0.26.0-beta.1 → 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.

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

When the hickory-resolver name server pool implementation receives an upstream response with the TC (truncated) header bit set, it re-queues the request to the same nameserver to retry with UDP transport disabled. However, the retry arm never inspects the transport that just answered and carries no iteration counter. An authoritative server that sets TC=1 on every available transport keeps the resolver spinning on one persistent TCP connection until the 5s per-request wall-clock deadline expires.

Reporter

Qifan Zhang, Palo Alto Networks

References

10 sources
hickory-dns/hickory-dns · security/advisories/GHSA-6w6g-hm98-mhgm
Vendor advisoryVulnCheck
hickory-dns/hickory-dns · pull request #3871
Patch
hickory-dns/hickory-dns · commit 0848d2e
Patch
hickory-dns/hickory-dns · commit 5d37e2e
Patch
hickory-dns/hickory-dns · repository
Source reference
hickory-dns/hickory-dns · releases/tag/v0.26.2
Release notes
View 4 more references
crates.io/crates/hickory-resolver
Source reference
rustsec.org/advisories/RUSTSEC-2026-0513.html
Security advisory
hickory-dns/hickory-dns · commit f9a7bc5
Patch
www.vulncheck.com/advisories/hickory-dns-0.26.0-beta.1-before-0.26.2-resource-exhaustion-dos-via-nameserverpool-try-send-tc-retry-loop
Security advisoryVulnCheck

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-2026-123604

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-835 ↗

Loop with Unreachable Exit Condition ('Infinite Loop')

VulnCheck

Related →
Contributing organizations · 2
VulnCheck

Assigning organization

2026-11-08
CISA-ADP

Additional data publisher

2026-11-12

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-2026-123604

    Observed 2026-11-13T01:26:13.468Z · upstream updated 2026-11-12T13:34:44.888Z

    Prioritization updated

    before

    []

    after

    [
  {
    "source": "CISA-ADP",
    "type": "SSVC",
    "role": "CISA Coordinator",
    "timestamp": "2026-11-12T13:34:10.429278Z",
    "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.