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GHSA-j382-5jj3-vw4j

Undertow HTTP server core doesn't properly validate the Host header in incoming HTTP requests

Source: GitHub Advisory Database (reviewed) Critical CVE-2025-12543

Packages

EcosystemPackageAffectedFixed in
Maven io.undertow:undertow-core 2.4.0.Alpha1 no fix listed
Maven io.undertow:undertow-core >= 2.3.0.Alpha1, < 2.3.21.Final 2.3.21.Final
Maven io.undertow:undertow-core < 2.2.39.Final 2.2.39.Final

Details

As written in the advisory (Markdown source, shown as plain text).

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.

References

External links from the advisory. They lead to third-party sites.