CVE-2026-28367 Undertow: undertow: request smuggling via `\r\r\r` as a header block terminator

High 8.7 Published 27 Mar 2026 Updated 14 Oct 2026

Remote attackers can perform request smuggling via malformed header terminators, leading to unauthorized access or request manipulation in Undertow.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-28367?

CVE-2026-28367 is a high-severity vulnerability in Redhat Jboss Enterprise Application Platform, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-444

Which versions are affected by CVE-2026-28367?

2 open source packages ship an affected version, including io.undertow:undertow-parent. It affects 9 products.

Package	Affected	Fixed in
`io.undertow:undertow-parent` Maven	All versions to `2.3.23.Final`	None
`io.undertow:undertow-parent` Maven	All versions to `2.3.23.Final`	None

Products include Redhat Build of Apache Camel - Hawtio, Redhat Build of Apache Camel for Spring Boot, Redhat Data Grid, Redhat Fuse, Redhat Jboss Enterprise Application Platform, Redhat Jboss Enterprise Application Platform Expansion Pack and 3 more.

How do I fix CVE-2026-28367?

Upgrade to a fixed version.

Is CVE-2026-28367 being exploited?

There is no known exploitation of CVE-2026-28367 in the wild and no public exploit code.

All Redhat Jboss Enterprise Application Platform vulnerabilities

Sources

Also known as DEBIAN-CVE-2026-28367, GHSA-3gv6-g396-9v4r, UBUNTU-CVE-2026-28367.