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

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-27 · updated 2026-10-30
Weakness: CWE-444

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 products

RedHat Build Of Apache Camel - Hawtio: 4.0 (and their updates)
RedHat Build Of Apache Camel For Spring Boot: 4.0 (and their updates)
RedHat Data Grid: 8.0 (and their updates)
Red Hat Fuse: 7.0.0 (and their updates)
Red Hat JBoss EAP: 7.0.0, 8.0.0 (and their updates)
RedHat Jboss Enterprise Application Platform Expansion Pack: all versions
RedHat Process Automation: 7.0 (and their updates)
Red Hat Single Sign-On: 7.0 (and their updates)
Red Hat undertow: all versions
Red Hat build of Apache Camel for Spring Boot 4: all versions
Red Hat Data Grid 8: all versions
Red Hat Fuse 7: all versions
Red Hat JBoss Enterprise Application Platform 7: all versions
Red Hat JBoss Enterprise Application Platform 8: all versions
Red Hat JBoss Enterprise Application Platform 8.1.6: all versions — fixed in 2.3.24.SP2-redhat-00001
Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8: all versions — fixed in 0:2.40.0-7.redhat_00015.1.el8eap
Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9: all versions — fixed in 0:2.40.0-7.redhat_00015.1.el9eap
Red Hat JBoss Enterprise Application Platform Expansion Pack: all versions
Red Hat Process Automation 7: all versions
Red Hat Single Sign-On 7: all versions

How to fix

Upgrade to a fixed version: Red Hat JBoss Enterprise Application Platform 8.1.6 2.3.24.SP2-redhat-00001; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 0:2.40.0-7.redhat_00015.1.el8eap; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 0:2.40.0-7.redhat_00015.1.el9eap. Check the vendor advisory for mitigations.

References

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