CVE-2025-12543

Medium

Elevated severity or exploit probability.

CVSS base

9.6 CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L

EPSS — probability of exploitation (30 days)

1.4%

70.3th percentile

CISA KEV

Not listed

Weakness / dates

CWE-20

Published 2026-01-07 · modified 2026-09-07

CVSS breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L

Attack Vector	N	Network
Attack Complexity	L	Low
Privileges Required	N	None
User Interaction	R	Required
Scope	C	Changed
Confidentiality	H	High
Integrity	H	High
Availability	L	Low

Timeline

2026-01-07 — Published (NVD)
2026-09-07 — Last modified (NVD)

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.

Affected

redhat

References

Official: NVD · CVE.org