CVE-2025-9784: Undertow core Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-95h4-w6j8-2rp8
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CVSS 7.5
CWE-404 CWE-770
Published
Advisory Summary

CVE-2025-9784 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-404: Improper Resource Shutdown or Release) affecting Undertow core libraries in the Maven ecosystem. The issue involves undertow madeyoureset http/2 ddos vulnerability. Remediation is available by upgrading affected packages to version 2.2.38.Final, 2.3.20.Final.

CVE-2025-9784 at a Glance

CVE Identifier CVE-2025-9784
GHSA Identifier GHSA-95h4-w6j8-2rp8
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-404: Improper Resource Shutdown or Release
Affected Product Undertow core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2025-9784

To remediate this vulnerability, upgrade all affected Undertow core dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

io.undertow:undertow-core fixed: 2.2.38.Final 
<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-core</artifactId>
    <version>2.2.38.Final</version>
</dependency>
io.undertow:undertow-core fixed: 2.3.20.Final 
<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-core</artifactId>
    <version>2.3.20.Final</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=io.undertow

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2025-9784, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=io.undertow

Analyze the terminal output to locate any version of Undertow core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.2.38.Final), your application is affected.

Note: The mvn dependency:tree -Dincludes=io.undertow command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-404: Improper Resource Shutdown or Release, where the product does not release or incorrectly releases a resource before it is made available for re-use. In Undertow core, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A flaw was found in Undertow where malformed client requests can trigger server-side stream resets without triggering abuse counters. This issue, referred to as the "MadeYouReset" attack, allows malicious clients to induce excessive server workload by repeatedly causing server-side stream aborts. While not a protocol bug, this highlights a common implementation weakness that can be exploited to cause a denial of service (DoS).

CVE-2025-9784 Affected Undertow core Versions

2 component(s)
Fixed Versions:
2.2.38.Final2.3.20.Final
Product / Package Ecosystem Affected Versions Fixed Version
io.undertow:undertow-core
maven/io.undertow/undertow-core
Maven
< 2.2.38.Final
2.2.38.Final
io.undertow:undertow-core
maven/io.undertow/undertow-core
Maven
≥ 2.3.0.Alpha1
< 2.3.20.Final
2.3.20.Final

References

NVD — CVE-2025-9784 NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-9784
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow/pull/1805
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow/pull/1804
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow/pull/1803
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow/pull/1802
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow/pull/1778
www.kb.cert.org/vuls/id/767506 WEB
https://www.kb.cert.org/vuls/id/767506
kb.cert.org/vuls/id/767506 WEB
https://kb.cert.org/vuls/id/767506
issues.redhat.com/browse/undertow-259... WEB
https://issues.redhat.com/browse/UNDERTOW-2598
Undertow core Release RELEASE
https://github.com/undertow-io/undertow/releases/tag/2.2.38.Final
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2392306
Undertow core Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2025-9784
access.redhat.com/errata/rhsa-2026:76... WEB
https://access.redhat.com/errata/RHSA-2026:76134
access.redhat.com/errata/rhsa-2026:76... WEB
https://access.redhat.com/errata/RHSA-2026:76132
access.redhat.com/errata/rhsa-2026:49... WEB
https://access.redhat.com/errata/RHSA-2026:4924
access.redhat.com/errata/rhsa-2026:49... WEB
https://access.redhat.com/errata/RHSA-2026:4917
access.redhat.com/errata/rhsa-2026:49... WEB
https://access.redhat.com/errata/RHSA-2026:4916
access.redhat.com/errata/rhsa-2026:49... WEB
https://access.redhat.com/errata/RHSA-2026:4915
access.redhat.com/errata/rhsa-2026:38... WEB
https://access.redhat.com/errata/RHSA-2026:3892
access.redhat.com/errata/rhsa-2026:38... WEB
https://access.redhat.com/errata/RHSA-2026:3891
access.redhat.com/errata/rhsa-2026:38... WEB
https://access.redhat.com/errata/RHSA-2026:3889
access.redhat.com/errata/rhsa-2026:33... WEB
https://access.redhat.com/errata/RHSA-2026:33372
access.redhat.com/errata/rhsa-2026:33... WEB
https://access.redhat.com/errata/RHSA-2026:33371
access.redhat.com/errata/rhsa-2026:03... WEB
https://access.redhat.com/errata/RHSA-2026:0386
access.redhat.com/errata/rhsa-2026:03... WEB
https://access.redhat.com/errata/RHSA-2026:0384
access.redhat.com/errata/rhsa-2026:03... WEB
https://access.redhat.com/errata/RHSA-2026:0383
access.redhat.com/errata/rhsa-2025:23... WEB
https://access.redhat.com/errata/RHSA-2025:23143

Frequently Asked Questions

What is CVE-2025-9784?
CVE-2025-9784 is a security vulnerability in Undertow core involving Undertow MadeYouReset HTTP/2 DDoS Vulnerability under CWE-404: Improper Resource Shutdown or Release.
Which Undertow core versions are affected?
Affected versions include releases prior to 2.2.38.Final, 2.3.20.Final across affected packages: io.undertow:undertow-core.
What version fixes CVE-2025-9784?
Upgrading to 2.2.38.Final, 2.3.20.Final (or the latest patched release for your respective branch) resolves the vulnerability.
Is undertow-core affected?
Yes, io.undertow:undertow-core is affected in releases prior to 2.2.38.Final, 2.3.20.Final. Upgrade your dependency to 2.2.38.Final, 2.3.20.Final or later.
What is the CVSS score of CVE-2025-9784?
CVE-2025-9784 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2025-9784?
CVE-2025-9784 is classified under CWE-404: Improper Resource Shutdown or Release (The product does not release or incorrectly releases a resource before it is made available for re-use.).
How can I check Maven dependencies for CVE-2025-9784?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=io.undertow'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
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    "url" : "https://access.redhat.com/errata/RHSA-2026:76134"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:76132"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:4924"
  }, {
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    "url" : "https://access.redhat.com/errata/RHSA-2026:4917"
  }, {
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    "url" : "https://access.redhat.com/errata/RHSA-2026:4916"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:4915"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3892"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3891"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3889"
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    "url" : "https://access.redhat.com/errata/RHSA-2026:33371"
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    "url" : "https://access.redhat.com/errata/RHSA-2026:0386"
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    "url" : "https://access.redhat.com/errata/RHSA-2026:0383"
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  "database_specific" : {
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    "github_reviewed_at" : "2025-09-02T20:54:27Z",
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  }
}