---
id: "CVE-2026-123604"
page: "https://infrastack.ai/live/CVE-2026-123604"
kind: "vulnerability"
aliases: ["CVE-2026-123604"]
title: "Hickory DNS resolver: unbounded retry loop lets a malicious DNS server exhaust resources"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["cargo", "dns", "hickory-resolver", "package", "rust"]
not_affected_if: ["no-hickory-resolver", "trusted-resolvers-only"]
published_at: "2026-11-08T02:16:55+00:00"
first_seen_at: "2026-11-08T02:21:14+00:00"
updated_at: "2026-11-08T02:22:47+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123604", "first_seen_at": "2026-11-08T02:21:14+00:00"}]
exploit_sources: []
---

# Hickory DNS resolver: unbounded retry loop lets a malicious DNS server exhaust resources

Link for people: https://infrastack.ai/live/CVE-2026-123604 (this .md is for agents)

hickory-resolver 0.26.0-beta.1 before 0.26.2 re-queues truncated DNS responses forever without counting attempts or checking the transport. A malicious authoritative DNS server that keeps sending truncated replies can make the resolver spin on a TCP connection until the 5-second deadline, exhausting resources.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the version of `hickory-resolver` in your lockfile (`Cargo.lock`) and look for `0.26.0-beta.1` or any version below `0.26.2`.
- Find whether your application uses the hickory-resolver crate directly or through another dependency (`cargo tree -i hickory-resolver`).

## Fix

- `hickory-resolver` `0.26.2` or later (the sources state the fix is in 0.26.2).

## Timeline

- 2026-11-08T02:21:14+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123604

## Documents

- [advisory] Vendor advisory: github.com https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-6w6g-hm98-mhgm
- [advisory] Third-party advisory: www.vulncheck.com https://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

## From the sources

Hickory DNS hickory-resolver 0.26.0-beta.1 before 0.26.2 contains an unbounded retry loop in NameServerPool::try_send, which re-queues truncated (TC) responses without checking the answering transport or counting iterations. A malicious authoritative server returning TC=1 on every transport keeps the resolver spinning on a persistent TCP connection until the 5-second request deadline expires, causing resource exhaustion.

---

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