---
id: CVE-2026-100658
title: >-
  Netty (io.netty:netty-codec-http) contains an unbounded per-connection queue
  in WebSocketServerExtensionHandler
summary: >-
  Netty (io.netty:netty-codec-http) contains an unbounded per-connection queue
  in WebSocketServerExtensionHandler. The handler offers an entry to its
  per-channel validExtensions queue for every inbound HttpRequest, but polls an
  entry only …
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-770
vendor: netty
product: netty
affected:
  - netty >= 4.1.88.Final < 4.1.138.Final
  - netty >= 4.2.0.Final < 4.2.18.Final
published: '2026-09-26'
updated: '2026-09-26'
sourceUpdated: '2026-09-26T14:16:48.687'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100658'
references:
  - url: 'https://github.com/netty/netty/security/advisories/GHSA-2g37-3h88-55hc'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/netty-before-4.1.138-final-denial-of-service-via-websocketserverextensionhandler
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-26T13:33:20.918Z'
---

## Overview

Netty (io.netty:netty-codec-http) contains an unbounded per-connection queue in WebSocketServerExtensionHandler. The handler offers an entry to its per-channel validExtensions queue for every inbound HttpRequest, but polls an entry only when the application writes an HttpResponse, and the queue size is never bounded. A remote, unauthenticated peer can use HTTP/1.1 pipelining to send requests faster than the application produces responses — including plain non-upgrade HTTP requests to any path — causing the queue to grow without limit until the JVM exhausts heap memory and terminates with OutOfMemoryError. Because the affected handler is the base class of WebSocketServerCompressionHandler, any server that enables permessage-deflate is exposed on its plain HTTP port before any WebSocket upgrade completes and before any application-level authentication. Affected versions are 4.1.88.Final through 4.1.137.Final and 4.2.0.Final through 4.2.17.Final; the issue is fixed in 4.1.138.Final and 4.2.18.Final.

## Remediation

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