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

High severity GitHub Reviewed Published Dec 3, 2025 to the GitHub Advisory Database • Updated Mar 18, 2026

Package

maven io.undertow:undertow-core (Maven)

Affected versions

= 2.4.0.Alpha1
< 2.2.39.Final
>= 2.3.0.Alpha1, < 2.3.21.Final

Patched versions

2.4.0.Beta1
2.2.39.Final
2.3.21.Final

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.

References

Published by the National Vulnerability Database Dec 3, 2025
Published to the GitHub Advisory Database Dec 3, 2025
Reviewed Jan 21, 2026
Last updated Mar 18, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(74th percentile)

Weaknesses

Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Learn more on MITRE.

CVE ID

CVE-2024-3884

GHSA ID

GHSA-6h4f-pj3g-q8fq

Source code

Credits

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