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Fencer Intel
high 8.7

CVE-2026-28367 json

Undertow: undertow: request smuggling via `\r\r\r` as a header block terminator

published 7mo ago modified 4d ago also EUVD-2026-16694 , GHSA-3gv6-g396-9v4r

cvss
8.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

Summary

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.

Patch / fix

  • maven io.undertow:undertow-core 2.2.40.Final, 2.3.25.Final
  • Red Hat Red Hat JBoss Enterprise Application Platform 8.1.6 2.3.24.SP2-redhat-00001
  • Red Hat Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 0:2.3.24-3.SP2_redhat_00001.1.el8eap, 0:2.40.0-7.redhat_00015.1.el8eap, 0:8.1.6-7.GA_redhat_00010.1.el8eap, 0:801.6.1-1.GA_redhat_00001.1.el8eap
  • Red Hat Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 0:2.3.24-3.SP2_redhat_00001.1.el9eap, 0:2.40.0-7.redhat_00015.1.el9eap, 0:8.1.6-7.GA_redhat_00010.1.el9eap, 0:801.6.1-1.GA_redhat_00001.1.el9eap
  • eap8-wildfly jboss enterprise application platform 8.1 8.1.6-7.GA_redhat_00010.1.el8eap
  • eap8-wildfly jboss enterprise application platform 8.1 8.1.6-7.GA_redhat_00010.1.el9eap
  • eap8-undertow jboss enterprise application platform 8.1 2.3.24-3.SP2_redhat_00001.1.el8eap
  • eap8-undertow jboss enterprise application platform 8.1 2.3.24-3.SP2_redhat_00001.1.el9eap
  • eap8-wildfly-modules jboss enterprise application platform 8.1 8.1.6-7.GA_redhat_00010.1.el8eap
  • eap8-wildfly-modules jboss enterprise application platform 8.1 8.1.6-7.GA_redhat_00010.1.el9eap
  • eap8-activemq-artemis jboss enterprise application platform 8.1 2.40.0-7.redhat_00015.1.el8eap
  • eap8-activemq-artemis jboss enterprise application platform 8.1 2.40.0-7.redhat_00015.1.el9eap

red hat advisories RHSA-2026:25125

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-28367 updated cvss 8.7

undertow: Undertow: Request smuggling via `\r\r\r` as a header block terminator

  • Red Hat build of Apache Camel for Spring Boot 4 undertow-core
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Data Grid 8 undertow-core Red Hat Fuse 7 undertow-core
    affected: workaround, no fix planned “Will not fix”
  • Red Hat JBoss Enterprise Application Platform 7 undertow-core Red Hat JBoss Enterprise Application Platform 8 undertow-core, org.jberet-jberet-parent Red Hat JBoss Enterprise Application Platform Expansion Pack org.jberet-jberet-parent, org.jboss.eap-jboss-eap-xp
    affected: workaround, no fix available
  • Red Hat Process Automation 7 undertow-core
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Single Sign-On 7 undertow-core
    affected: workaround, no fix available “Fix deferred”
  • Red Hat JBoss EAP 8.1 for RHEL 8 eap8-wildfly 8.1.6-7.GA_redhat_00010.1.el8eap, eap8-undertow 2.3.24-3.SP2_redhat_00001.1.el8eap, eap8-activemq-artemis 2.40.0-7.redhat_00015.1.el8eap, eap8-wildfly-modules 8.1.6-7.GA_redhat_00010.1.el8eap, eap8-activemq-artemis-cli 2.40.0-7.redhat_00015.1.el8eap, eap8-activemq-artemis-dto 2.40.0-7.redhat_00015.1.el8eap, +16 more Red Hat JBoss EAP 8.1 for RHEL 9 eap8-wildfly 8.1.6-7.GA_redhat_00010.1.el9eap, eap8-undertow 2.3.24-3.SP2_redhat_00001.1.el9eap, eap8-activemq-artemis 2.40.0-7.redhat_00015.1.el9eap, eap8-wildfly-modules 8.1.6-7.GA_redhat_00010.1.el9eap, eap8-activemq-artemis-cli 2.40.0-7.redhat_00015.1.el9eap, eap8-activemq-artemis-dto 2.40.0-7.redhat_00015.1.el9eap, +16 more
    fixed: vendor fix RHSA-2026:25125
  • Red Hat JBoss Enterprise Application Platform 8.1.6 undertow-core 2.3.24.SP2-redhat-00001
    fixed: vendor fix RHSA-2026:25126
  • Red Hat build of Apache Camel - HawtIO 4 undertow-core
    not affected: vulnerable code not in execute path
show 1 more
  • Red Hat Enterprise Linux 8 resteasy, resteasy-javadoc Red Hat Enterprise Linux 9 resteasy, pki-resteasy-core, pki-resteasy-client, pki-resteasy-jackson2-provider, pki-resteasy-servlet-initializer Red Hat Enterprise Linux 10 moditect Red Hat JBoss Enterprise Application Platform 8.1.6 pom.xml, aesh 2.4, c3 0.6.4, d3 7.4.3, he 1.2.0, lr 1.4.2, +1868 more Red Hat JBoss Enterprise Application Platform Expansion Pack undertow-core
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
7mo ago

Exploit prediction

0.72% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 8.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
GitHub 3.1 8.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
NVD 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
maven io.undertow:undertow-core
>=2.3.0.Final, <2.3.25.Final
<2.2.40.Final
2.3.25.Final
2.2.40.Final

Affected products

  • 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

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.