# CVE-2024-4027: Undertow: outofmemoryerror in httpservletrequestimpl.getparameternames() can cause remote dos attacks

> An attacker can cause a remote denial of service by sending requests with large parameter names, triggering an OutOfMemoryError 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:** 30 Jan 2026
- **Updated:** 1 Sep 2026
- **Also known as:** CLSA-2026-1778546708, CLSA-2026-1784769562, DEBIAN-CVE-2024-4027, GHSA-33hj-rcmx-86mv, UBUNTU-CVE-2024-4027

## What is CVE-2024-4027?

CVE-2024-4027 is a high-severity denial of service vulnerability in Red Hat Data Grid 8, published on 30 Jan 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. Servlets using a method that calls HttpServletRequestImpl.getParameterNames() can cause an OutOfMemoryError when the client sends a request with large parameter names. This issue can be exploited by an unauthorized user to cause a remote denial-of-service (DoS) attack.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2024-4027?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.undertow:undertow-core` | Maven | All versions | 2.2.39.Final |
| `io.undertow:undertow-core` | Maven | All versions | 2.2.39.Final |
| `io.undertow:undertow-core` | Maven | From 2.3.0.Alpha1 | 2.3.21.Final |
| `io.undertow:undertow-core` | Maven | From 2.3.0.Alpha1 | 2.3.21.Final |
| `io.undertow:undertow-core` | Maven | From 2.4.0.Alpha1 | 2.4.0.Beta1 |
| `io.undertow:undertow-core` | Maven | From 2.4.0.Alpha1 | 2.4.0.Beta1 |

## How do I fix CVE-2024-4027?

Upgrade io.undertow:undertow-core to a fixed version for your release line: 2.2.39.Final, 2.3.21.Final or 2.4.0.Beta1.

## Is CVE-2024-4027 being exploited?

There is no known exploitation of CVE-2024-4027 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-4027 and fix it if it is affected.

What it is: CVE-2024-4027 is a high-severity denial of service vulnerability in Red Hat Data Grid 8, published on 30 Jan 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-2024-4027 in the wild and no public exploit code.

Affected packages and fixed versions:
- io.undertow:undertow-core (Maven): affected all versions; fixed in 2.2.39.Final
- io.undertow:undertow-core (Maven): affected all versions; fixed in 2.2.39.Final
- io.undertow:undertow-core (Maven): affected from 2.3.0.Alpha1; fixed in 2.3.21.Final
- io.undertow:undertow-core (Maven): affected from 2.3.0.Alpha1; fixed in 2.3.21.Final
- io.undertow:undertow-core (Maven): affected from 2.4.0.Alpha1; fixed in 2.4.0.Beta1
- io.undertow:undertow-core (Maven): affected from 2.4.0.Alpha1; fixed in 2.4.0.Beta1

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-2024-4027/ (Markdown: https://insights.sbomify.com/CVE-2024-4027/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-4027
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-4027
- OSV: https://osv.dev/vulnerability/CVE-2024-4027

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-4027/
Summaries are generated and may contain mistakes; the official description above is the record.