CVE-2026-28369: Undertow parent Undertow Is Vulnerable To HTTP Vulnerability

HIGH
Advisory Identifier: GHSA-vqqj-9cmv-hx43
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CVSS 8.7
CWE-444
Published
Advisory Summary

CVE-2026-28369 is a HIGH (CVSS 8.7) undertow is vulnerable to http vulnerability (CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')) affecting Undertow parent libraries in the Maven ecosystem. The issue involves undertow is vulnerable to http request/response smuggling. Remediation is available in the latest vendor maintenance releases.

CVE-2026-28369 at a Glance

CVE Identifier CVE-2026-28369
GHSA Identifier GHSA-vqqj-9cmv-hx43
Severity HIGH
CVSS v3.1 Base Score 8.7
CWE Classification CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Affected Product Undertow parent
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 8.7

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

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

How to Fix CVE-2026-28369

To remediate this vulnerability, upgrade all affected Undertow parent 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-parent fixed: Latest secure release 
<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-parent</artifactId>
    <version>Latest secure release</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-2026-28369, 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 parent in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), 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-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'), where the product acts as an intermediary http agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed http requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. In Undertow parent, 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. When Undertow receives an HTTP request where the first header line starts with one or more spaces, it incorrectly processes the request by stripping these leading spaces. This behavior, which violates HTTP standards, can be exploited by a remote attacker to perform request smuggling. Request smuggling allows an attacker to bypass security mechanisms, access restricted information, or manipulate web caches, potentially leading to unauthorized actions or data exposure.

CVE-2026-28369 Affected Undertow parent Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
io.undertow:undertow-parent
maven/io.undertow/undertow-parent
Maven
≤ 2.3.23.Final

References

NVD — CVE-2026-28369 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28369
access.redhat.com/errata/rhsa-2026:25... WEB
https://access.redhat.com/errata/RHSA-2026:25125
access.redhat.com/errata/rhsa-2026:25... WEB
https://access.redhat.com/errata/RHSA-2026:25126
Undertow parent Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-28369
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2443262
Undertow parent Source Repository REPOSITORY
https://github.com/undertow-io/undertow

Frequently Asked Questions

What is CVE-2026-28369?
CVE-2026-28369 is a security vulnerability in Undertow parent involving Undertow is Vulnerable to HTTP Request/Response Smuggling under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling').
Which Undertow parent versions are affected?
Affected versions include releases prior to current release patches across affected packages: io.undertow:undertow-parent.
What version fixes CVE-2026-28369?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is undertow-parent affected?
Yes, io.undertow:undertow-parent is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-28369?
CVE-2026-28369 has a CVSS v3.1 base score of 8.7 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N.
What CWE is associated with CVE-2026-28369?
CVE-2026-28369 is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') (The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.).
How can I check Maven dependencies for CVE-2026-28369?
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 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vqqj-9cmv-hx43",
  "modified" : "2026-06-11T00:32:03Z",
  "published" : "2026-03-27T18:31:27Z",
  "aliases" : [ "CVE-2026-28369" ],
  "summary" : "Undertow is Vulnerable to HTTP Request/Response Smuggling",
  "details" : "A flaw was found in Undertow. When Undertow receives an HTTP request where the first header line starts with one or more spaces, it incorrectly processes the request by stripping these leading spaces. This behavior, which violates HTTP standards, can be exploited by a remote attacker to perform request smuggling. Request smuggling allows an attacker to bypass security mechanisms, access restricted information, or manipulate web caches, potentially leading to unauthorized actions or data exposure.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.undertow:undertow-parent"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "2.3.23.Final"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-28369"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:25125"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:25126"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-28369"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2443262"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/undertow-io/undertow"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-444" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-31T23:14:40Z",
    "nvd_published_at" : "2026-03-27T17:16:28Z"
  }
}