---
id: CVE-2026-100659
title: >-
  Netty's HTTP/3 codec (io.netty:netty-codec-http3) in versions 4.2.0.Final
  through 4.2.17.Final does not enforce the RFC 9114 requirement that the
  :authority pseudo-header field and a literal host header field, when both
  present, carry th…
summary: >-
  Netty's HTTP/3 codec (io.netty:netty-codec-http3) in versions 4.2.0.Final
  through 4.2.17.Final does not enforce the RFC 9114 requirement that the
  :authority pseudo-header field and a literal host header field, when both
  present, carry th…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-444
vendor: netty
product: netty
affected:
  - netty >= 4.2.0.Final < 4.2.18.Final
published: '2026-09-26'
updated: '2026-09-26'
sourceUpdated: '2026-09-26T14:16:48.830'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100659'
references:
  - url: 'https://github.com/netty/netty/security/advisories/GHSA-q9pg-8h3j-8hvm'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/netty-4.2.0-through-4.2.18-http-3-request-routing-bypass
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-26T13:33:20.915Z'
---

## Overview

Netty's HTTP/3 codec (io.netty:netty-codec-http3) in versions 4.2.0.Final through 4.2.17.Final does not enforce the RFC 9114 requirement that the :authority pseudo-header field and a literal host header field, when both present, carry the same value. A remote unauthenticated peer can send a single HEADERS frame containing both fields with differing, attacker-controlled values; the request is accepted and delivered to the application with two conflicting authorities, allowing routing, virtual-host, and access-control decisions to be bypassed when different components in the request path consult different fields. This issue is fixed in 4.2.18.Final.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.