---
id: CVE-2026-100665
title: >-
  Netty versions from 4.2.11.Final before 4.2.18.Final contain an incomplete
  hostname verification fix in the QUIC certificate verification path when using
  a plain X509TrustManager
summary: >-
  Netty versions from 4.2.11.Final before 4.2.18.Final contain an incomplete
  hostname verification fix in the QUIC certificate verification path when using
  a plain X509TrustManager. The BoringSSLCertificateVerifyCallback discards the
  SSLEn…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-295
vendor: netty
product: netty
affected:
  - netty >= 4.2.11.Final < 4.2.18.Final
published: '2026-09-26'
updated: '2026-10-02'
sourceUpdated: '2026-10-02T16:16:41.803'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100665'
references:
  - url: >-
      https://github.com/netty/netty/commit/09e72c4fd8007277121ed48db63a124b112b96fe
    label: disclosure@vulncheck.com
  - url: 'https://github.com/netty/netty/commit/994e887ed9'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/netty/netty/security/advisories/GHSA-mj35-3qqm-q387'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/netty-4.2.11-through-4.2.17-quic-hostname-verification-bypass
    label: disclosure@vulncheck.com
  - url: 'https://github.com/netty/netty/security/advisories/GHSA-mj35-3qqm-q387'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-100665.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-100665'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2541820'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-100665'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100665'
tags:
  - nvd
  - cve.org
  - exploit-available
  - csaf
  - vex
  - red-hat
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-02T15:46:31.371553Z'
epss: 0.00367
epssPercentile: 0.30429
ingestedAt: '2026-09-26T13:33:20.915Z'
---

## Overview

Netty versions from 4.2.11.Final before 4.2.18.Final contain an incomplete hostname verification fix in the QUIC certificate verification path when using a plain X509TrustManager. The BoringSSLCertificateVerifyCallback discards the SSLEngine for plain trust managers, preventing endpoint identification from running even when HTTPS verification is configured. Attackers on the network path can present a certificate chain for the wrong hostname that the plain trust manager accepts, bypassing hostname authentication for QUIC clients.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat OpenShift Dev Spaces · no fix planned: Red Hat OpenShift Dev Spaces · updated 2026-09-29 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-100665.json)