CVE-2025-12543

Publication date 7 January 2026

Last updated 2 April 2026

Ubuntu priority

Cvss 3 Severity Score

Description

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.

Why is this CVE high priority?

user sesison takeover

Learn more about Ubuntu priority

Status

Show unmaintained releases

Package	Ubuntu Release	Status
undertow	25.10 questing	Vulnerable
	25.04 plucky	Ignored end of life, was needs-triage
	24.04 LTS noble	Fixed 2.3.8-2ubuntu0.1~esm1
	22.04 LTS jammy	Fixed 2.2.16-1ubuntu0.1~esm1
	20.04 LTS focal	Fixed 2.0.29-1ubuntu0.1~esm1
	18.04 LTS bionic	Fixed 1.4.23-3ubuntu0.1~esm1
	16.04 LTS xenial	Fixed 1.3.16-1ubuntu0.1~esm1

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Severity score breakdown

Parameter	Value
Base score	9.6 · Critical
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	Required
Scope	Changed
Confidentiality	High
Integrity impact	High
Availability impact	Low
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L

References

Related Ubuntu Security Notices (USN)

USN-8144-1
Undertow vulnerability
2 April 2026