Undertow Host Header Validation Flaw Enables Cache Poisoning
CVE-2025-12543 Published on January 7, 2026
Undertow-core: undertow http server fails to reject malformed host headers leading to potential cache poisoning and ssrf
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.
Vulnerability Analysis
CVE-2025-12543 can be exploited with network access, requires user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and a small impact on availability.
Timeline
Reported to Red Hat.
Made public. 69 days later.
Weakness Type
Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
Products Associated with CVE-2025-12543
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Affected Versions
Red Hat JBoss Enterprise Application Platform 8.1: Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8:- Version 0:4.0.10-1.redhat_00001.1.el8eap and below * is unaffected.
- Version 0:1.82.0-1.redhat_00001.1.el8eap and below * is unaffected.
- Version 0:801.3.0-1.GA_redhat_00001.1.el8eap and below * is unaffected.
- Version 0:1.0.1-3.redhat_00003.1.el8eap and below * is unaffected.
- Version 0:6.6.36-1.Final_redhat_00001.1.el8eap and below * is unaffected.
- Version 0:4.0.2-1.Final_redhat_00001.1.el8eap and below * is unaffected.
- Version 0:2.5.0-1.redhat_00001.1.el8eap and below * is unaffected.
- Version 0:2.3.20-2.SP4_redhat_00001.1.el8eap and below * is unaffected.
- Version 0:8.1.3-4.GA_redhat_00006.1.el8eap and below * is unaffected.
- Version 0:5.0.12-1.Final_redhat_00001.1.el8eap and below * is unaffected.
- Version 0:2.6.6-1.Final_redhat_00001.1.el8eap and below * is unaffected.
- Version 0:8.1.1-4.GA_redhat_00007.1.el8eap and below * is unaffected.
- Version 0:4.0.10-1.redhat_00001.1.el9eap and below * is unaffected.
- Version 0:1.82.0-1.redhat_00001.1.el9eap and below * is unaffected.
- Version 0:801.3.0-1.GA_redhat_00001.1.el9eap and below * is unaffected.
- Version 0:1.0.1-3.redhat_00003.1.el9eap and below * is unaffected.
- Version 0:6.6.36-1.Final_redhat_00001.1.el9eap and below * is unaffected.
- Version 0:4.0.2-1.Final_redhat_00001.1.el9eap and below * is unaffected.
- Version 0:2.5.0-1.redhat_00001.1.el9eap and below * is unaffected.
- Version 0:2.3.20-2.SP4_redhat_00001.1.el9eap and below * is unaffected.
- Version 0:8.1.3-4.GA_redhat_00006.1.el9eap and below * is unaffected.
- Version 0:5.0.12-1.Final_redhat_00001.1.el9eap and below * is unaffected.
- Version 0:2.6.6-1.Final_redhat_00001.1.el9eap and below * is unaffected.
- Version 0:8.1.1-4.GA_redhat_00007.1.el9eap and below * is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.