# CVE-2025-12543

## Summary

- **CVE ID:** CVE-2025-12543
- **Severity:** CRITICAL
- **CVSS Score:** 9.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L)
- **CWE:** CWE-20
- **Published:** Jan 7, 2026
- **Last Modified:** Sep 7, 2026

## 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 Products

- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8 (0:1.83.0-1.redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8 (0:33.0.0-2.jre_redhat_00003.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8 (0:4.0.6-1.redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8 (0:1.0.0-3.redhat_00009.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8 (0:2.0.2-1.Final_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8 (0:2.3.23-1.SP3_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 9 (0:1.83.0-1.redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 9 (0:33.0.0-2.jre_redhat_00003.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 9 (0:4.0.6-1.redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 9 (0:1.0.0-3.redhat_00009.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 9 (0:2.0.2-1.Final_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 9 (0:2.3.23-1.SP3_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:4.0.10-1.redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:1.82.0-1.redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:801.3.0-1.GA_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:1.0.1-3.redhat_00003.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:6.6.36-1.Final_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:4.0.2-1.Final_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:2.5.0-1.redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:2.3.20-2.SP4_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:8.1.3-4.GA_redhat_00006.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:5.0.12-1.Final_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:2.6.6-1.Final_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (0:8.1.1-4.GA_redhat_00007.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:4.0.10-1.redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:1.82.0-1.redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:801.3.0-1.GA_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:1.0.1-3.redhat_00003.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:6.6.36-1.Final_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:4.0.2-1.Final_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:2.5.0-1.redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:2.3.20-2.SP4_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:8.1.3-4.GA_redhat_00006.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:5.0.12-1.Final_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:2.6.6-1.Final_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 (0:8.1.1-4.GA_redhat_00007.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7 (0:2.2.39-1.Final_redhat_00001.1.el7eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7 (0:7.4.24-4.GA_redhat_00002.1.el7eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 8 (0:2.2.39-1.Final_redhat_00001.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 8 (0:7.4.24-4.GA_redhat_00002.1.el8eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 9 (0:2.2.39-1.Final_redhat_00001.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 9 (0:7.4.24-4.GA_redhat_00002.1.el9eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform (2.2.39.Final-redhat-00001)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.1 EUS for RHEL 7 (0:1.4.18-21.SP19_redhat_00001.1.ep7.el7)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.3 EUS for RHEL 7 (0:2.0.41-8.SP9_redhat_00001.1.el7eap)
- Red Hat — Red Hat JBoss Enterprise Application Platform 7.4.24 (2.2.39.Final-redhat-00001)
- Red Hat — Red Hat JBoss Enterprise Application Platform 8.1.6 (2.3.24.SP2-redhat-00001)

## References

- [CNA](https://access.redhat.com/errata/RHSA-2026:0383)
- [CNA](https://access.redhat.com/errata/RHSA-2026:0384)
- [CNA](https://access.redhat.com/errata/RHSA-2026:0386)
- [CNA](https://access.redhat.com/errata/RHSA-2026:3889)
- [CNA](https://access.redhat.com/errata/RHSA-2026:3890)
- [CNA](https://access.redhat.com/errata/RHSA-2026:3891)
- [CNA](https://access.redhat.com/errata/RHSA-2026:3892)
- [CNA](https://access.redhat.com/security/cve/CVE-2025-12543)
- [CNA](https://bugzilla.redhat.com/show_bug.cgi?id=2408784)
- [CNA](https://access.redhat.com/errata/RHSA-2026:4915)
- [CNA](https://access.redhat.com/errata/RHSA-2026:4916)
- [CNA](https://access.redhat.com/errata/RHSA-2026:4917)
- [CNA](https://access.redhat.com/errata/RHSA-2026:4924)
- [CNA](https://access.redhat.com/errata/RHSA-2026:33371)
- [CNA](https://access.redhat.com/errata/RHSA-2026:33372)
- [redhat-SADP](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-12543.json)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 1.35%
- **EPSS Percentile:** 70.1

---
_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._