GHSA-6w6g-hm98-mhgm: hickory-resolver Remote Code Execution Vulnerability

HIGH
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CWE-406 CWE-400 CWE-835
Published
Advisory Summary

GHSA-6w6g-hm98-mhgm is a HIGH remote code execution vulnerability (CWE-406: Insufficient Control of Network Message Volume (Network Amplification)) affecting hickory-resolver libraries in the crates.io ecosystem. The issue involves unbounded tc-retry loop in `nameserverpool::try_send` (resource-exhaustion dos). Remediation is available by upgrading affected packages to version 0.26.2.

GHSA-6w6g-hm98-mhgm at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-6w6g-hm98-mhgm
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-406: Insufficient Control of Network Message Volume (Network Amplification)
Affected Product hickory-resolver
Package Ecosystem crates.io
Published Date
Last Updated

How to Fix GHSA-6w6g-hm98-mhgm

To remediate this vulnerability, upgrade all affected hickory-resolver dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

hickory-resolver fixed: 0.26.2 
Upgrade hickory-resolver to 0.26.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for hickory-resolver

How to Check if You Are Affected

To determine whether your application is affected by GHSA-6w6g-hm98-mhgm, inspect your project dependencies for hickory-resolver:

inspect dependencies for hickory-resolver

Analyze the terminal output to locate any version of hickory-resolver in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.26.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-406: Insufficient Control of Network Message Volume (Network Amplification), where the product does not sufficiently monitor or control transmitted network traffic volume, so that an actor can cause the product to transmit more traffic than should be allowed for that actor. In hickory-resolver, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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

GHSA-6w6g-hm98-mhgm Affected hickory-resolver Versions

1 component(s)
Fixed Versions:
0.26.2
Product / Package Ecosystem Affected Versions Fixed Version
hickory-resolver
 crates.io
≥ 0.26.0-beta.1
< 0.26.2
0.26.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-6w6g-hm98-mhgm
hickory-resolver Source Repository REPOSITORY
https://github.com/hickory-dns/hickory-dns/pull/3871
Security Fix Commit FIX COMMIT
https://github.com/hickory-dns/hickory-dns/commit/0848d2e9e4183499343318a690d6dd5e48bc21c1
Security Fix Commit FIX COMMIT
https://github.com/hickory-dns/hickory-dns/commit/5d37e2e04a36a87013a213b58b820345ef76a263
hickory-resolver Source Repository REPOSITORY
https://github.com/hickory-dns/hickory-dns
hickory-resolver Release RELEASE
https://github.com/hickory-dns/hickory-dns/releases/tag/v0.26.2

Frequently Asked Questions

What is GHSA-6w6g-hm98-mhgm?
GHSA-6w6g-hm98-mhgm is a security vulnerability in hickory-resolver involving Unbounded TC-retry loop in `NameServerPool::try_send` (resource-exhaustion DoS) under CWE-406: Insufficient Control of Network Message Volume (Network Amplification).
Which hickory-resolver versions are affected?
Affected versions include releases prior to 0.26.2 across affected packages: hickory-resolver.
What version fixes GHSA-6w6g-hm98-mhgm?
Upgrading to 0.26.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hickory-resolver affected?
Yes, hickory-resolver is affected in releases prior to 0.26.2. Upgrade your dependency to 0.26.2 or later.
What CWE is associated with GHSA-6w6g-hm98-mhgm?
GHSA-6w6g-hm98-mhgm is classified under CWE-406: Insufficient Control of Network Message Volume (Network Amplification) (The product does not sufficiently monitor or control transmitted network traffic volume, so that an actor can cause the product to transmit more traffic than should be allowed for that actor.).
How can I check crates.io dependencies for GHSA-6w6g-hm98-mhgm?
Run the dependency tree command: 'inspect dependencies for hickory-resolver'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6w6g-hm98-mhgm",
  "modified" : "2026-10-05T22:55:10Z",
  "published" : "2026-10-05T22:55:10Z",
  "aliases" : [ ],
  "summary" : "hickory-resolver: Unbounded TC-retry loop in `NameServerPool::try_send` (resource-exhaustion DoS)",
  "details" : "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.\n\n### Reporter\n\nQifan Zhang, Palo Alto Networks",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "hickory-resolver"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.26.0-beta.1"
      }, {
        "fixed" : "0.26.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-6w6g-hm98-mhgm"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hickory-dns/hickory-dns/pull/3871"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hickory-dns/hickory-dns/commit/0848d2e9e4183499343318a690d6dd5e48bc21c1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hickory-dns/hickory-dns/commit/5d37e2e04a36a87013a213b58b820345ef76a263"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/hickory-dns/hickory-dns"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hickory-dns/hickory-dns/releases/tag/v0.26.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-406", "CWE-835" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-05T22:55:10Z",
    "nvd_published_at" : null
  }
}