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
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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2024-3884 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
io.undertow:undertow-core☕io.undertow:undertow-core☕io.undertow:undertow-coreReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.undertow:undertow-core | all versions | 2.2.39.Finalio.undertow:undertow-core:2.2.39.Final |
| ☕Maven | io.undertow:undertow-core | ≥ 2.4.0.Alpha1&&< 2.4.0.Beta1 | 2.4.0.Beta1io.undertow:undertow-core:2.4.0.Beta1 |
| ☕Maven | io.undertow:undertow-core | ≥ 2.3.0.Alpha1&&< 2.3.21.Final | 2.3.21.Finalio.undertow:undertow-core:2.3.21.Final |
Detection & mitigation playbook
Open-source dependencyDetect
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2024-3884 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-3884. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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 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.
| 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
Is CVE-2024-3884 in your dependencies?
O3 Security finds CVE-2024-3884 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.