Improper Input Validation Affecting undertow package, versions <2.3.8-2ubuntu0.1~esm1


Severity

Recommended
high

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.05% (15th percentile)

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  • Snyk IDSNYK-UBUNTU2404-UNDERTOW-14905933
  • published6 Apr 2026
  • disclosed7 Jan 2026

Introduced: 7 Jan 2026

CVE-2025-12543  (opens in a new tab)
CWE-20  (opens in a new tab)

How to fix?

Upgrade Ubuntu:24.04 undertow to version 2.3.8-2ubuntu0.1~esm1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream undertow package and not the undertow package as distributed by Ubuntu. See How to fix? for Ubuntu:24.04 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1