Undertow: undertow: request smuggling via `\r\r\r` as a header block terminator
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.
- Published
- Mar 27, 2026
- Updated
- Sep 21, 2026
- EPSS
- 0.9% · 58th percentile
- CWE
- CWE-444
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Report tools
Action score
36
Monitor
Low priority for now.
- CVSS
- 36 / 40 · 9.1 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.9%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 9.1
- CNA · redhat
- 8.7
- 0.4 point gap
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
| Vendor | Product | CPE |
|---|---|---|
| redhat | build of apache camel - hawtio | cpe:2.3:a:redhat:build_of_apache_camel_-_hawtio |
| redhat | build of apache camel for spring boot | cpe:2.3:a:redhat:build_of_apache_camel_for_spring_boot |
| redhat | data grid | cpe:2.3:a:redhat:data_grid |
| redhat | fuse | cpe:2.3:a:redhat:fuse |
| redhat | jboss enterprise application platform | cpe:2.3:a:redhat:jboss_enterprise_application_platform |
| redhat | jboss enterprise application platform expansion pack | cpe:2.3:a:redhat:jboss_enterprise_application_platform_expansion_pack |
| redhat | process automation | cpe:2.3:a:redhat:process_automation |
| redhat | single sign-on | cpe:2.3:a:redhat:single_sign-on |
| redhat | undertow | cpe:2.3:a:redhat:undertow |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- redhat build of apache camel - hawtio4.0
- redhat build of apache camel for spring boot4.0
- redhat data grid8.0
- redhat fuse7.0.0
- redhat jboss enterprise application platform7.0.0
- redhat jboss enterprise application platform8.0.0
- redhat jboss enterprise application platform expansion packall versions
- redhat process automation7.0
- redhat single sign-on7.0
- redhat undertowall versions
Versions reported by the vendor
Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.
Red Hat Red Hat build of Apache Camel - HawtIO 4
- all versionsunknown
Red Hat Red Hat build of Apache Camel for Spring Boot 4
- all versionsaffected
Red Hat Red Hat Data Grid 8
- all versionsaffected
Red Hat Red Hat Enterprise Linux 10
- all versionsunknown
Red Hat Red Hat Enterprise Linux 8
- all versionsunknown
- all versionsunknown
Red Hat Red Hat Enterprise Linux 9
- all versionsunknown
Red Hat Red Hat Fuse 7
- all versionsaffected
Red Hat Red Hat JBoss Enterprise Application Platform 7
- all versionsaffected
Red Hat Red Hat JBoss Enterprise Application Platform 8
- all versionsaffected
- all versionsaffected
Red Hat Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8
- 0:2.40.0-7.redhat_00015.1.el8eap and laternot affected · rpm
- 0:801.6.1-1.GA_redhat_00001.1.el8eap and laternot affected · rpm
- 0:2.3.24-3.SP2_redhat_00001.1.el8eap and laternot affected · rpm
- 0:8.1.6-7.GA_redhat_00010.1.el8eap and laternot affected · rpm
Red Hat Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9
- 0:2.40.0-7.redhat_00015.1.el9eap and laternot affected · rpm
- 0:801.6.1-1.GA_redhat_00001.1.el9eap and laternot affected · rpm
- 0:2.3.24-3.SP2_redhat_00001.1.el9eap and laternot affected · rpm
- 0:8.1.6-7.GA_redhat_00010.1.el9eap and laternot affected · rpm
Red Hat Red Hat JBoss Enterprise Application Platform 8.1.7.GA
- 2.3.24.SP3-redhat-00001 and laternot affected · rpm
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:14 | undertow | all versions | — |
| Maven | io.undertow:undertow-parent | up to and including 2.3.23.Final | — |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-cli | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-commons | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-core-client | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-dto | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-hornetq-protocol | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-hqclient-protocol | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jakarta-client | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jakarta-ra | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jakarta-server | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jakarta-service-extensions | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-jdbc-store | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-journal | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-selector | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-activemq-artemis-server | before 0:2.40.0-7.redhat_00015.1.el8eap | 0:2.40.0-7.redhat_00015.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-eap-product-conf-parent | before 0:801.6.1-1.GA_redhat_00001.1.el8eap | 0:801.6.1-1.GA_redhat_00001.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-eap-product-conf-wildfly-ee-feature-pack | before 0:801.6.1-1.GA_redhat_00001.1.el8eap | 0:801.6.1-1.GA_redhat_00001.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-undertow | before 0:2.3.24-3.SP2_redhat_00001.1.el8eap | 0:2.3.24-3.SP2_redhat_00001.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-wildfly | before 0:8.1.6-7.GA_redhat_00010.1.el8eap | 0:8.1.6-7.GA_redhat_00010.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-wildfly-java-jdk17 | before 0:8.1.6-7.GA_redhat_00010.1.el8eap | 0:8.1.6-7.GA_redhat_00010.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-wildfly-java-jdk21 | before 0:8.1.6-7.GA_redhat_00010.1.el8eap | 0:8.1.6-7.GA_redhat_00010.1.el8eap |
| Red Hat:jboss_enterprise_application_platform:8.1::el8 | eap8-wildfly-modules | before 0:8.1.6-7.GA_redhat_00010.1.el8eap | 0:8.1.6-7.GA_redhat_00010.1.el8eap |
+22
Same product
redhat: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-28369Undertow: undertow: request smuggling via malformed http request headers36Monitor
- CVE-2026-28368Undertow: undertow: request smuggling via inconsistent header parsing36Monitor
- CVE-2024-7885Undertow: improper state management in proxy protocol parsing causes information leakage31Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| red hat:eap8-activemq-artemis | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-cli | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-commons | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-core-client | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-dto | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-hornetq-protocol | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-hqclient-protocol | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-jakarta-client | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-jakarta-ra | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-jakarta-server | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-jakarta-service-extensions | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
| red hat:eap8-activemq-artemis-jdbc-store | 0:2.40.0-7.redhat_00015.1.el8eap · Red Hat:jboss_enterprise_application_platform:8.1::el8 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-283680 days apartUndertow: undertow: request smuggling via inconsistent header parsing36Monitor
- CVE-2026-283690 days apartUndertow: undertow: request smuggling via malformed http request headers36Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- None
Weakness class (CWE)
CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
—
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- access.redhat.com/errata/RHSA-2026:25125
- access.redhat.com/errata/RHSA-2026:25126
- access.redhat.com/security/cve/CVE-2026-28367
- bugzilla.redhat.com/show_bug.cgi?id=2443260
Vendor advisories and official records. Exploit/PoC links are deliberately left out.