How severe is CVE-2024-3884?

CVE-2024-3884 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2024-3884?

CVE-2024-3884 affects the following packages: io.undertow:undertow-core (Maven), io.undertow:undertow-core (Maven), io.undertow:undertow-core (Maven). Ecosystems affected: Maven.

How do I fix CVE-2024-3884?

Update io.undertow:undertow-core to 2.2.39.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-3884 is resolved across your whole dependency graph.

How do I detect CVE-2024-3884 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.undertow:undertow-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2024-3884 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2024-3884 actively exploited in the wild?

No public exploit code has been indexed for CVE-2024-3884 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2024-3884?

CVE-2024-3884 has an EPSS (Exploit Prediction Scoring System) score of 1.5%, placing it in the 74th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2024-3884?

CVE-2024-3884 is classified as Improper Input Validation (CWE-20). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2024-3884 published, and has it been updated?

CVE-2024-3884 was published on December 3, 2025 and was last updated on September 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

CVE-2024-3884 — undertow-core

HIGHFix: undertow-io/undertow#1894

CVE-2024-3884 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in io.undertow:undertow-core. A fix is available for io.undertow:undertow-core — see the affected versions and patch details below.

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

Published

Dec 3, 2025

Updated

Sep 10, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2024-3884.

EPSS Exploitation Probability

via FIRST.org ↗

1.5%probability of exploitation in next 30 days

Lower Risk+0.10%

Lower risk than most CVEs74th percentile — riskier than 74% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected

☕io.undertow:undertow-core☕io.undertow:undertow-core☕io.undertow:undertow-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.undertow:undertow-core`	all versions	2.2.39.Final`io.undertow:undertow-core:2.2.39.Final`
☕Maven	`io.undertow:undertow-core`	≥ 2.4.0.Alpha1&&< 2.4.0.Beta1	2.4.0.Beta1`io.undertow:undertow-core:2.4.0.Beta1`
☕Maven	`io.undertow:undertow-core`	≥ 2.3.0.Alpha1&&< 2.3.21.Final	2.3.21.Final`io.undertow:undertow-core:2.3.21.Final`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.undertow:undertow-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.undertow:undertow-core to 2.2.39.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-3884 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Red Hat rates this as a Moderate impact since this requires the use of a specific form method by the server that must be externally available and the input is not sanitized by the given servlet or class implementing its use.

Workaround published by Red Hat

It is possible to mitigate the vulnerability by performing an upper-level verification to ensure the content size sent server side is within the allowed parameters.

Source: Red Hat security advisory for CVE-2024-3884 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat JBoss Enterprise Application Platform 7.1 EUS for RHEL 7	`eap7-undertow-0:1.4.18-19.SP17_redhat_00001.1.ep7.el7`	RHSA-2026:6012
Red Hat JBoss Enterprise Application Platform 7.3 EUS for RHEL 7	`eap7-undertow-0:2.0.41-7.SP8_redhat_00001.1.el7eap`	RHSA-2026:6011
Red Hat JBoss Enterprise Application Platform 7.4.24	`io.undertow/undertow-core:2.2.39.Final-redhat-00001`	RHSA-2026:4924
Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7	`eap7-undertow-0:2.2.39-1.Final_redhat_00001.1.el7eap`	RHSA-2026:4915
Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 8	`eap7-undertow-0:2.2.39-1.Final_redhat_00001.1.el8eap`	RHSA-2026:4916
Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 9	`eap7-undertow-0:2.2.39-1.Final_redhat_00001.1.el9eap`	RHSA-2026:4917
Red Hat JBoss Enterprise Application Platform 8.0	`undertow`	RHSA-2026:3892
Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8	`eap8-bouncycastle-0:1.83.0-1.redhat_00001.1.el8eap`	RHSA-2026:3889

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2024-3884 in your dependencies?

Find it across Maven, including transitive dependencies.

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