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HIGH severity

CVE-2026-28367 — undertow-parent

HIGH

CVE-2026-28367 is a high-severity (CVSS 8.7) CWE-444 vulnerability in io.undertow:undertow-parent. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Undertow is Vulnerable to HTTP Request/Response Smuggling

Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 25, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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 CVE-2026-28367.

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk-0.17%
Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk
0.00%0.46%0.93%1.39%0.0%0.7%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
☕io.undertow:undertow-parent

Real-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 Undertow. A remote attacker can exploit this vulnerability by sending \r\r\r as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer, potentially leading to unauthorized access or manipulation of web requests.

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
☕Mavenio.undertow:undertow-parentall versionsNo fix

Affected Products

9 products · 10 configurations
Application
build of apache camel - hawtioredhat
1 version
4.0
Application
build of apache camel for spring bootredhat
1 version
4.0
Application
data gridredhat
1 version
8.0
Application
fuseredhat
1 version
7.0.0
Application
jboss enterprise application platformredhat
2 versions
7.0.08.0.0
Application
jboss enterprise application platform expansion packredhat
all

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.undertow:undertow-parent, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    The records we use list no patched version of io.undertow:undertow-parent for CVE-2026-28367. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    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.

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.

Red HatImportant

The Undertow web server is susceptible to request smuggling when deployed with certain proxy servers that forward `\r\r\r` as a header block terminator. This flaw could enable an attacker to manipulate web requests, potentially leading to unauthorized access. Red Hat products using Undertow in environments with…

Workaround published by Red Hat
To mitigate this vulnerability, configure any proxy servers positioned in front of Undertow to strictly validate HTTP header terminations. Ensure that these proxies are configured to reject or normalize non-standard header block terminators, such as `\r\r\r`, before forwarding requests to Undertow. This operational control helps prevent request smuggling attacks by ensuring that only properly formed HTTP requests reach the Undertow server.
Source: Red Hat security advisory for CVE-2026-28367 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat JBoss Enterprise Application Platform 8.1.6io.undertow/undertow-core:2.3.24.SP2-redhat-00001RHSA-2026:25126
Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8eap8-activemq-artemis-0:2.40.0-7.redhat_00015.1.el8eapRHSA-2026:25125

Frequently Asked Questions

A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending `\r\r\r` as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer, potentially leading to unauthorized access or manipulation of web requests.
O3 Security · Impact-Aware SCA

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CVE-2026-28367: undertow-parent (High 8.7)