How severe is CVE-2026-19204?

CVE-2026-19204 has a CVSS 4.0 base score of 8.7, rated high severity.

Is CVE-2026-19204 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-19204?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-19204 published?

CVE-2026-19204 was published on 2026-09-07 and last updated on 2026-09-08.

CVE-2026-19204

CVE-2026-19204 is a high-severity vulnerability with a CVSS 4.0 base score of 8.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-770.

Key facts

Severity: High (CVSS 4.0 base score 8.7)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-770
Published: 2026-09-07
Last modified: 2026-09-08

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.

Frequently asked questions

What is 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 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.
How severe is CVE-2026-19204?: CVE-2026-19204 has a CVSS 4.0 base score of 8.7, rated high severity.
Is CVE-2026-19204 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-19204?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-19204 published?: CVE-2026-19204 was published on 2026-09-07 and last updated on 2026-09-08.

References

https://github.com/jetty/jetty.project/security/advisories/GHSA-85fq-fc5f-7j7g

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