High severity · published Sep 7, 2026
CVE-2026-19204
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…
8.7
CVSS
0.5%
EPSS
No
On KEV
Description
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 39% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
EJ
Eclipse Jetty · Eclipse Foundation
12.1.0 through 12.1.11; 12.0.0 through 12.0.37; 11.0.0 through 11.0.31; 10.0.0 through 10.0.31 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-19204
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-19204
github.com
https://github.com/jetty/jetty.project/security/advisories/GHSA-85fq-fc5f-7j7g
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