---
id: CVE-2026-100655
title: >-
  Netty (io.netty:netty-codec-http) versions up to and including 4.1.137.Final
  and from 4.2.0.Final through 4.2.17.Final accept an unlimited number of
  concurrent remote-initiated SPDY streams: SpdySessionHandler defaults
  localConcurrentStr…
summary: >-
  Netty (io.netty:netty-codec-http) versions up to and including 4.1.137.Final
  and from 4.2.0.Final through 4.2.17.Final accept an unlimited number of
  concurrent remote-initiated SPDY streams: SpdySessionHandler defaults
  localConcurrentStr…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-770
vendor: netty
product: netty
affected:
  - netty < 4.1.138.Final
  - netty >= 4.2.0.Final < 4.2.18.Final
published: '2026-09-26'
updated: '2026-09-26'
sourceUpdated: '2026-09-26T14:16:48.243'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100655'
references:
  - url: 'https://github.com/netty/netty/security/advisories/GHSA-rmcw-9fcq-wjq7'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/netty-before-4.1.138-final-denial-of-service-via-spdysessionhandler
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-26T13:33:20.917Z'
---

## Overview

Netty (io.netty:netty-codec-http) versions up to and including 4.1.137.Final and from 4.2.0.Final through 4.2.17.Final accept an unlimited number of concurrent remote-initiated SPDY streams: SpdySessionHandler defaults localConcurrentStreams to Integer.MAX_VALUE and exposes no API to change it. A remote peer that opens a SPDY connection and sends millions of SYN_STREAM frames with FLAG_FIN=0 causes the server to allocate unbounded heap and direct memory, eventually triggering a JVM OutOfMemoryError and crashing the service. 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.