CVE-2026-28368: Red Hat Undertow request smuggling via inconsistent header parsing

CVE-2026-28368 · Severity: high · CVSS 8.7 · Published 2026-03-27

Undertow, a web server component used in Red Hat JBoss and other Java applications, is vulnerable to a security flaw in how it handles web requests. By sending specially crafted messages, an attacker can trick the server into misinterpreting where one request ends and another begins. This can allow unauthorized users to bypass security filters, access private data, or interfere with other users' sessions.

Technologies: io.undertow:undertow-parent (Maven). Vendors: Maven.

Quick answers

Is CVE-2026-28368 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-28368 being exploited in the wild.
How severe is CVE-2026-28368?
High severity, with a CVSS score of 8.7, published 27 March 2026.
Which products and versions are affected?
io.undertow:undertow-parent (Maven) <= 2.3.23.Final, ECOSYSTEM:introduced=0,last_affected=2.3.23.Final.
Is there a fix for CVE-2026-28368?
A patch was published on 2026-06-10: Red Hat released security updates (RHSA-2026:25125, RHSA-2026:25126) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-28368 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-28368?
Check whether you run io.undertow:undertow-parent (Maven) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A flaw exists in Undertow's HTTP header parsing logic (CWE-444). The server splits header names from values using either a space or a colon, whichever appears first. This behavior differs from standard upstream proxies, allowing an attacker to craft requests with headers that are interpreted by Undertow but ignored by the proxy. This discrepancy enables HTTP request smuggling. An attacker can use this to bypass security constraints, poison web caches, or hijack user sessions. The vulnerability is addressed in Undertow version 2.3.24.SP2 and Red Hat JBoss EAP 8.1.6.

Affected products

  • Red Hat Undertow <= 2.3.23.Final
  • Red Hat JBoss Enterprise Application Platform 7.0, 8.0, 8.1.0

Identifiers

  • CVE-2026-28368
  • GHSA-8v4x-mgvp-p658

Timeline

  • 2026-02-27: disclosed: Initial report in Red Hat Bugzilla
  • 2026-03-27: advisory: GitHub and NVD advisories published
  • 2026-06-10: patched: Red Hat released security updates (RHSA-2026:25125, RHSA-2026:25126)

References

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