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Fencer Intel
high 8.7

CVE-2026-19204 json

A client may send a WebSocket frame with an unknown opcode and a very large declared payload length, causing Jetty to attempt a large memor…

published 2mo ago modified 2mo ago also EUVD-2026-72335

cvss
8.7
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 39%
public exploits
0
none known

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

Patch / fix

  • jetty12 Debian 14 12.0.39-1

debian advisories DEBIAN-CVE-2026-19204

Is CVE-2026-19204 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-19204 updated cvss 7.5

org.eclipse.jetty.websocket/websocket-core-common: Jetty: Denial of Service via crafted WebSocket frame with unknown opcode

  • Red Hat Enterprise Linux 9 jmc Red Hat Satellite 6 puppetserver
    affected: workaround, no fix available
  • Red Hat Fuse 7 websocket-core-common
    not affected: vulnerable code cannot be controlled by adversary

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2mo ago

Exploit prediction

0.45% chance of exploitation in the next 30 days, higher than 39% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 8.7 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
CNA 4.0 8.7 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • Eclipse Foundation Eclipse Jetty

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling
  • CWE-789 Memory Allocation with Excessive Size Value

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.