Undertow OutOfMemory when parsing form data encoding with application/x-www-form-urlencoded

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2024-3884: 1.46% estimated exploitation activity in the next 30 days; percentile 73.53 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

A flaw was found in Undertow that can cause remote denial of service attacks. When the server uses the FormEncodedDataDefinition.doParse(StreamSourceChannel) method to parse large form data encoding with application/x-www-form-urlencoded, the method will cause an OutOfMemory issue. This flaw allows unauthorized users to cause a remote denial of service (DoS) attack.

Published by the source

3 Dec 2025, 21:31 UTC

Last modified by the source

30 Mar 2026, 12:33 UTC

Source last checked

26 Oct 2026, 16:44 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6h4f-pj3g-q8fq

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# Patch Next advisory brief: CVE-2024-3884

Advisory: Undertow OutOfMemory when parsing form data encoding with application/x-www-form-urlencoded
IDs: CVE-2024-3884, GHSA-6h4f-pj3g-q8fq
Record: https://patchnext.com/advisories/cve-2024-3884 (revision 1, source checked 26 Oct 2026, 16:44 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: io.undertow:undertow-core 2.4.0.Beta1, 2.3.21.Final, 2.2.39.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.undertow:undertow-core: affected >= 2.4.0.Alpha1, <= 2.4.0.Alpha1; < 2.2.39.Final; >= 2.3.0.Alpha1, < 2.3.21.Final; fixed in 2.2.39.Final, 2.3.21.Final, 2.4.0.Beta1

## Suggested inspection (read-only)
- Maven io.undertow:undertow-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on io.undertow:undertow-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6h4f-pj3g-q8fq (GitHub-reviewed advisory GHSA-6h4f-pj3g-q8fq lists affected ranges: Maven io.undertow:undertow-core >=2.4.0.Alpha1 =0 =2.3.0.Alpha1 <2.3.21.Final)

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