# CVE-2026-19204: Denial of service in Eclipse Jetty

> Attackers can exhaust JVM heap memory via crafted WebSocket frames when auto-fragmentation is enabled, causing denial of service in Jetty servers.

- **Severity:** High 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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** CLEANSTART-2026-SV46004, CLEANSTART-2026-TT31497, CLEANSTART-2026-VO81158, DEBIAN-CVE-2026-19204, GHSA-85fq-fc5f-7j7g, GHSA-w753-5ffq-99wr, UBUNTU-CVE-2026-19204

## What is CVE-2026-19204?

CVE-2026-19204 is a high-severity denial of service vulnerability in Eclipse Jetty, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-789 (Memory Allocation with Excessive Size Value), CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-19204?


## How do I fix CVE-2026-19204?

Apply the vendor's patch.

## Is CVE-2026-19204 being exploited?

There is no known exploitation of CVE-2026-19204 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19204 and fix it if it is affected.

What it is: CVE-2026-19204 is a high-severity denial of service vulnerability in Eclipse Jetty, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-19204 in the wild and no public exploit code.

Affected product: Eclipse Jetty. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-19204/ (Markdown: https://insights.sbomify.com/CVE-2026-19204/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19204
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19204
- OSV: https://osv.dev/vulnerability/CVE-2026-19204

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19204/
Summaries are generated and may contain mistakes; the official description above is the record.