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
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Red Hat | Red Hat JBoss Enterprise Application Platform 8.1.6 | — | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 | — | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 | — | — |
| Red Hat | Red Hat build of Apache Camel for Spring Boot 4 | — | — |
| Red Hat | Red Hat build of Apache Camel - HawtIO 4 | — | — |
| Red Hat | Red Hat Data Grid 8 | — | — |
| Red Hat | Red Hat Enterprise Linux 10 | — | — |
| Red Hat | Red Hat Enterprise Linux 8 | — | — |
| Red Hat | Red Hat Enterprise Linux 9 | — | — |
| Red Hat | Red Hat Fuse 7 | — | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 7 | — | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 8 | — | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform Expansion Pack | — | — |
| Red Hat | Red Hat Process Automation 7 | — | — |
| Red Hat | Red Hat Single Sign-On 7 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | undertow | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | undertow | No fix yet | — |
| Ubuntu 26.04 LTS | undertow | No fix yet | — |
| Ubuntu 25.10 | undertow | No fix yet | — |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 24.04 LTS | undertow | No fix yet | — |
| Ubuntu Pro 22.04 LTS | undertow | No fix yet | — |
| Ubuntu Pro 20.04 LTS | undertow | No fix yet | — |
| Ubuntu Pro 18.04 LTS | undertow | No fix yet | — |
| Ubuntu Pro 16.04 LTS | undertow | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat JBoss EAP 8 | eap8-activemq-artemis +14 | 2.40.0-7.redhat_00015.1.el8eap | RHSA-2026:25125 |
| Red Hat JBoss EAP 8 | eap8-eap-product-conf-parent +1 | 801.6.1-1.GA_redhat_00001.1.el8eap | RHSA-2026:25125 |
| Red Hat JBoss EAP 8 | eap8-undertow | 2.3.24-3.SP2_redhat_00001.1.el8eap | RHSA-2026:25125 |
| Red Hat JBoss EAP 8 | eap8-wildfly +3 | 8.1.6-7.GA_redhat_00010.1.el8eap | RHSA-2026:25125 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Maven | io.undertow:undertow-core | >= 2.3.0.Final, < 2.3.25.Final | 2.3.25.Final | GHSA-3gv6-g396-9v4r |
| Maven | io.undertow:undertow-core | < 2.2.40.Final | 2.2.40.Final | GHSA-3gv6-g396-9v4r |
Advisories 2
- RHSA-2026:25125 Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 8.1.6 security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- WID-SEC-2026-0907 Red Hat Undertow: Mehrere Schwachstellen ermöglichen Umgehung von Sicherheitsmaßnahmen BSI CERT-Bund (WID) · Jun 10, 2026
References
- RHSA-2026:25125 vendor-advisory
- RHSA-2026:25126 vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-28367 vdb-entry
- RHBZ#2443260 issue-tracking