---
id: CVE-2026-19204
title: >-
  A client may send a WebSocket frame with an unknown opcode and a very large
  declared payload length, causing Jetty to attempt a large memory allocation
  and potentially exhaust the JVM heap.





  This occurs when auto-fragmentation is enab…
summary: >-
  A client may send a WebSocket frame with an unknown opcode and a very large
  declared payload length, causing Jetty to attempt a large memory allocation
  and potentially exhaust the JVM heap.





  This occurs when auto-fragmentation is enab…
severity: high
cvss: 8.7
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
cwe:
  - CWE-770
  - CWE-789
  - CWE-1284
vendor: Eclipse Foundation
product: Eclipse Jetty
affected:
  - eclipse_jetty >= 12.1.0 <= 12.1.11
  - eclipse_jetty >= 12.0.0 <= 12.0.37
  - eclipse_jetty >= 11.0.0 <= 11.0.31
  - eclipse_jetty >= 10.0.0 <= 10.0.31
published: '2026-09-07'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T16:18:06.627'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-19204'
references:
  - url: >-
      https://github.com/jetty/jetty.project/security/advisories/GHSA-85fq-fc5f-7j7g
    label: emo@eclipse.org
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-19204.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-19204'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2529344'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-19204'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-19204'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-08T15:06:34.664874Z'
cvssSource: cna
epss: 0.0031
epssPercentile: 0.21273
ingestedAt: '2026-09-08T15:33:26.976Z'
scores:
  cna: 8.7
  vendor: 7.5
---

## Overview

A client may send a WebSocket frame with an unknown opcode and a very large declared payload length, causing Jetty to attempt a large memory allocation and potentially exhaust the JVM heap.




This occurs when auto-fragmentation is enabled, as unknown opcodes bypass the normal maximum frame size handling and payload allocation occurs before the opcode is validated.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 9, Red Hat Satellite 6 · no fix planned: Red Hat Enterprise Linux 9, Red Hat Satellite 6 · updated 2026-09-25 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-19204.json)