Vulnerabilities CVE-2025-12543

CVE-2025-12543

Critical

Open

TLP:CLEAR

Undertow-core: undertow http server fails to reject malformed host headers leading to potential cache poisoning and ssrf

NVD CVE.org

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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.

Details

CVSS Score: 9.6
EPSS Score ⓘ: 1.20%

65.4th percentile
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L
Confidence: 90%
Published: Jan 7, 2026
Last Modified: Aug 10, 2026

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