GHSA-j382-5jj3-vw4j is a critical-severity (CVSS 9.6) Improper Input Validation vulnerability in io.undertow:undertow-core. A fix is available for io.undertow:undertow-core — see the affected versions and patch details below.
Undertow HTTP server core doesn't properly validate the Host header in incoming HTTP requests
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-j382-5jj3-vw4j.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-j382-5jj3-vw4j plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
io.undertow:undertow-core☕io.undertow:undertow-core☕io.undertow:undertow-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.undertow:undertow-core | all versions | No fix |
| ☕Maven | io.undertow:undertow-core | ≥ 2.3.0.Alpha1&&< 2.3.21.Final | 2.3.21.Finalio.undertow:undertow-core:2.3.21.Final |
| ☕Maven | io.undertow:undertow-core | all versions | 2.2.39.Finalio.undertow:undertow-core:2.2.39.Final |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.undertow:undertow-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
No patched version of io.undertow:undertow-core has shipped for GHSA-j382-5jj3-vw4j yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-j382-5jj3-vw4j can be triaged on real exposure rather than presence alone.
Tailored to GHSA-j382-5jj3-vw4j. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability has an Important severity because it can be remotely exploited without authentication. However, limited user interaction is required for full impact. It could allow attackers to hijack additional accounts, steal credentials, or gain access to internal systems. The issue stems from improper input…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use, applicability, or stability.Source: Red Hat security advisory for GHSA-j382-5jj3-vw4j (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat build of Apache Camel 4.14.4 for Spring Boot 3.5.11 | undertow-core | RHSA-2026:3890 |
| Red Hat JBoss Enterprise Application Platform 7.1 EUS for RHEL 7 | eap7-undertow-0:1.4.18-21.SP19_redhat_00001.1.ep7.el7 | RHSA-2026:33372 |
| Red Hat JBoss Enterprise Application Platform 7.3 EUS for RHEL 7 | eap7-undertow-0:2.0.41-8.SP9_redhat_00001.1.el7eap | RHSA-2026:33371 |
| Red Hat JBoss Enterprise Application Platform 7.4.24 | io.undertow/undertow-core:2.2.39.Final-redhat-00001 | RHSA-2026:4924 |
| Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7 | eap7-undertow-0:2.2.39-1.Final_redhat_00001.1.el7eap | RHSA-2026:4915 |
| Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 8 | eap7-undertow-0:2.2.39-1.Final_redhat_00001.1.el8eap | RHSA-2026:4916 |
| Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 9 | eap7-undertow-0:2.2.39-1.Final_redhat_00001.1.el9eap | RHSA-2026:4917 |
| Red Hat JBoss Enterprise Application Platform 8.0 | undertow-core | RHSA-2026:3892 |
Frequently Asked Questions
Is GHSA-j382-5jj3-vw4j in your dependencies?
O3 Security finds GHSA-j382-5jj3-vw4j across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.