CVE-2025-12543: Undertow core Undertow HTTP Server Core Doesn't Vulnerability

CRITICAL
Advisory Identifier: GHSA-j382-5jj3-vw4j
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CVSS 9.6
CWE-20
Published
Advisory Summary

CVE-2025-12543 is a CRITICAL (CVSS 9.6) undertow http server core doesn't vulnerability (CWE-20: Improper Input Validation) affecting Undertow core libraries in the Maven ecosystem. The issue involves undertow http server core doesn't properly validate the host header in incoming http requests. Remediation is available by upgrading affected packages to version 2.3.21.Final, 2.2.39.Final.

CVE-2025-12543 at a Glance

CVE Identifier CVE-2025-12543
GHSA Identifier GHSA-j382-5jj3-vw4j
Severity CRITICAL
CVSS v3.1 Base Score 9.6
CWE Classification CWE-20: Improper Input Validation
Affected Product Undertow core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.6

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:R/S:C/C:H/I:H/A:L).

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

How to Fix CVE-2025-12543

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: Latest secure release 
<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-core</artifactId>
    <version>Latest secure release</version>
</dependency>
io.undertow:undertow-core fixed: 2.3.21.Final 
<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-core</artifactId>
    <version>2.3.21.Final</version>
</dependency>
io.undertow:undertow-core fixed: 2.2.39.Final 
<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-core</artifactId>
    <version>2.2.39.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-2025-12543, 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 2.3.21.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-20: Improper Input Validation, where 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. 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 the Undertow HTTP server core, which is used in WildFly, JBoss EAP, and other Java applications. The Undertow library fails to properly validate the Host header in incoming HTTP requests. As a result, requests containing malformed or malicious Host headers are processed without rejection, enabling attackers to poison caches, perform internal network scans, or hijack user sessions.

CVE-2025-12543 Affected Undertow core Versions

3 component(s)
Fixed Versions:
2.3.21.Final2.2.39.Final
Product / Package Ecosystem Affected Versions Fixed Version
io.undertow:undertow-core
maven/io.undertow/undertow-core
Maven
2.4.0.Alpha1
All 1 versions
2.4.0.Alpha1
None specified
io.undertow:undertow-core
maven/io.undertow/undertow-core
Maven
≥ 2.3.0.Alpha1
< 2.3.21.Final
2.3.21.Final
io.undertow:undertow-core
maven/io.undertow/undertow-core
Maven
< 2.2.39.Final
2.2.39.Final

References

access.redhat.com/errata/rhsa-2026:38... WEB
https://access.redhat.com/errata/RHSA-2026:3889
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-2026:3890
access.redhat.com/errata/rhsa-2026:03... WEB
https://access.redhat.com/errata/RHSA-2026:0384
access.redhat.com/errata/rhsa-2026:49... WEB
https://access.redhat.com/errata/RHSA-2026:4915
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-2026:0383
NVD — CVE-2025-12543 NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-12543
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow/pull/1860
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow/pull/1857
issues.redhat.com/browse/undertow-265... WEB
https://issues.redhat.com/browse/UNDERTOW-2656
Undertow core Release RELEASE
https://github.com/undertow-io/undertow/releases/tag/2.3.21.Final
Undertow core Release RELEASE
https://github.com/undertow-io/undertow/releases/tag/2.2.39.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=2408784
Undertow core Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2025-12543
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-2026:38... WEB
https://access.redhat.com/errata/RHSA-2026:3892

Frequently Asked Questions

What is CVE-2025-12543?
CVE-2025-12543 is a security vulnerability in Undertow core involving Undertow HTTP server core doesn't properly validate the Host header in incoming HTTP requests under CWE-20: Improper Input Validation.
Which Undertow core versions are affected?
Affected versions include releases prior to 2.3.21.Final, 2.2.39.Final across affected packages: io.undertow:undertow-core.
What version fixes CVE-2025-12543?
Upgrading to 2.3.21.Final, 2.2.39.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 Latest secure release, 2.3.21.Final, 2.2.39.Final. Upgrade your dependency to Latest secure release, 2.3.21.Final, 2.2.39.Final or later.
What is the CVSS score of CVE-2025-12543?
CVE-2025-12543 has a CVSS v3.1 base score of 9.6 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L.
What CWE is associated with CVE-2025-12543?
CVE-2025-12543 is classified under CWE-20: 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.).
How can I check Maven dependencies for CVE-2025-12543?
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-j382-5jj3-vw4j",
  "modified" : "2026-03-18T18:31:10Z",
  "published" : "2026-01-07T18:30:25Z",
  "aliases" : [ "CVE-2025-12543" ],
  "summary" : "Undertow HTTP server core doesn't properly validate the Host header in incoming HTTP requests",
  "details" : "A flaw was found in the Undertow HTTP server core, which is used in WildFly, JBoss EAP, and other Java applications. The Undertow library fails to properly validate the Host header in incoming HTTP requests. As a result, requests containing malformed or malicious Host headers are processed without rejection, enabling attackers to poison caches, perform internal network scans, or hijack user sessions.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.undertow:undertow-core"
    },
    "versions" : [ "2.4.0.Alpha1" ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.undertow:undertow-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.3.0.Alpha1"
      }, {
        "fixed" : "2.3.21.Final"
      } ]
    } ]
  }, {
    "package" : {
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      "name" : "io.undertow:undertow-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
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        "introduced" : "0"
      }, {
        "fixed" : "2.2.39.Final"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-12543"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/undertow-io/undertow/pull/1860"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/undertow-io/undertow/pull/1857"
  }, {
    "type" : "WEB",
    "url" : "https://issues.redhat.com/browse/UNDERTOW-2656"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/undertow-io/undertow/releases/tag/2.3.21.Final"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/undertow-io/undertow/releases/tag/2.2.39.Final"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/undertow-io/undertow"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2408784"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2025-12543"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:4924"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:4917"
  }, {
    "type" : "WEB",
    "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-2026:3890"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3889"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:0386"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:0384"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:0383"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-01-08T17:15:55Z",
    "nvd_published_at" : "2026-01-07T17:15:55Z"
  }
}