# CVE-2026-3260: Undertow: Denial of Service via Multipart/Form-Data Parsing on HTTP GET Requests


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 24 Mar 2026
- **Updated:** 7 Jul 2026
- **Also known as:** CLEANSTART-2026-DD15041, GHSA-3x3v-w654-m28m

## What is CVE-2026-3260?

CVE-2026-3260 is a vulnerability in io.undertow:undertow-core, published on 24 Mar 2026. 

### Official description

The Undertow web server enforces a default maximum HTTP request entity size limit. Any request (including GET or HEAD) containing a body that exceeds this configurable limit is safely dropped by the server, preventing single-request Resource Exhaustion (Out of Memory) Denial of Service attacks.

## Which versions are affected by CVE-2026-3260?

2 open source packages ship an affected version, including io.undertow:undertow-core.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.undertow:undertow-core` | Maven | All versions | None |
| `io.undertow:undertow-core` | Maven | All versions | None |

## How do I fix CVE-2026-3260?

Upgrade to a fixed version.

## Is CVE-2026-3260 being exploited?

There is no known exploitation of CVE-2026-3260 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3260 and fix it if it is affected.

What it is: CVE-2026-3260 is a vulnerability in io.undertow:undertow-core, published on 24 Mar 2026. 
Exploitation: There is no known exploitation of CVE-2026-3260 in the wild and no public exploit code.

Affected packages and fixed versions:
- io.undertow:undertow-core (Maven): affected all versions; no fix listed
- io.undertow:undertow-core (Maven): affected all versions; no fix listed

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-2026-3260/ (Markdown: https://insights.sbomify.com/CVE-2026-3260/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3260
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3260
- OSV: https://osv.dev/vulnerability/CVE-2026-3260

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3260/
Summaries are generated and may contain mistakes; the official description above is the record.