# CVE-2026-15565: Denial of service in Red Hat Data Grid 8

> Remote attackers can cause denial of service via memory exhaustion on unauthenticated WebSocket endpoints in Undertow.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-15565, GHSA-356w-cx4r-75hv, UBUNTU-CVE-2026-15565

## What is CVE-2026-15565?

CVE-2026-15565 is a high-severity denial of service vulnerability in Red Hat Data Grid 8, published on 11 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in Undertow. A remote attacker can cause Out of Memory on websockets endpoint without authentication on any @ServerEndpoint class that has any @OnMessage method. This allows an attacker to cause Denial of Service attack without authentication and using only a standard WebSocket handshake.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2026-15565?


## How do I fix CVE-2026-15565?

Apply the vendor's patch.

## Is CVE-2026-15565 being exploited?

There is no known exploitation of CVE-2026-15565 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-15565 and fix it if it is affected.

What it is: CVE-2026-15565 is a high-severity denial of service vulnerability in Red Hat Data Grid 8, published on 11 Aug 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-2026-15565 in the wild and no public exploit code.

Affected product: Red Hat Data Grid 8. 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-2026-15565/ (Markdown: https://insights.sbomify.com/CVE-2026-15565/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-15565
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15565
- OSV: https://osv.dev/vulnerability/CVE-2026-15565

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-15565/
Summaries are generated and may contain mistakes; the official description above is the record.