CriticalCVE-2026-28369

    Undertow: undertow: request smuggling via malformed http request headers (CVE-2026-28369)

    Published Last modified Sources: BSI, CVE.org, OSV

    What is affected, what to do

    A flaw was found in Undertow. When Undertow receives an HTTP request where the first header line starts with one or more spaces, it incorrectly processes the request by stripping these leading spaces.

    Update Red Hat JBoss Enterprise Application Platform 8.1.6 to version 2.3.24.SP2-redhat-00001, Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 to version 0:2.40.0-7.redhat_00015.1.el8eap, Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 to version 0:801.6.1-1.GA_redhat_00001.1.el8eap.

    Affected
    • Red Hat JBoss Enterprise Application Platform 8.1.6 lt *..2.3.24.SP2-redhat-00001
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 lt *..0:2.40.0-7.redhat_00015.1.el8eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 lt *..0:801.6.1-1.GA_redhat_00001.1.el8eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 lt *..0:2.3.24-3.SP2_redhat_00001.1.el8eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 lt *..0:8.1.6-7.GA_redhat_00010.1.el8eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 lt *..0:2.40.0-7.redhat_00015.1.el9eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 lt *..0:801.6.1-1.GA_redhat_00001.1.el9eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 lt *..0:2.3.24-3.SP2_redhat_00001.1.el9eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 lt *..0:8.1.6-7.GA_redhat_00010.1.el9eap
    Fixed in
    • 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 8 0:801.6.1-1.GA_redhat_00001.1.el8eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 0:2.3.24-3.SP2_redhat_00001.1.el8eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 0:8.1.6-7.GA_redhat_00010.1.el8eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 0:2.40.0-7.redhat_00015.1.el9eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 0:801.6.1-1.GA_redhat_00001.1.el9eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 0:2.3.24-3.SP2_redhat_00001.1.el9eap
    • Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 0:8.1.6-7.GA_redhat_00010.1.el9eap

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    Metrics

    9.1

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    8.7

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: BSI, CVE.org, OSV

    0.9 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 58.6

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    86.87 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.1 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.7
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.9 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    58.6
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-444

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    A flaw was found in Undertow. When Undertow receives an HTTP request where the first header line starts with one or more spaces, it incorrectly processes the request by stripping these leading spaces. This behavior, which violates HTTP standards, can be exploited by a remote attacker to perform request smuggling. Request smuggling allows an attacker to bypass security mechanisms, access restricted information, or manipulate web caches, potentially leading to unauthorized actions or data exposure.

    Source: BSI CSAF, BSI WID Portal, NVD (NIST), OSV (Open Source Vulnerabilities), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    VendorProductAffected versionsFixed in
    Red HatRed Hat build of Apache Camel - HawtIO 4
    • —
    • —
    Red HatRed Hat build of Apache Camel for Spring Boot 4
    • —
    • —
    Red HatRed Hat Data Grid 8
    • —
    • —
    Red HatRed Hat Enterprise Linux 10
    • —
    • —
    Red HatRed Hat Enterprise Linux 8
    • —
    • —
    Red HatRed Hat Enterprise Linux 9
    • —
    • —
    Red HatRed Hat Fuse 7
    • —
    • —
    Red HatRed Hat JBoss Enterprise Application Platform 7
    • —
    • —
    Red HatRed Hat JBoss Enterprise Application Platform 8
    • —
    • —
    Red HatRed Hat JBoss Enterprise Application Platform 8.1 for RHEL 8
    • < 0:2.40.0-7.redhat_00015.1.el8eap
    • < 0:2.3.24-3.SP2_redhat_00001.1.el8eap
    • < 0:8.1.6-7.GA_redhat_00010.1.el8eap
    • < 0:801.6.1-1.GA_redhat_00001.1.el8eap
    • 0:2.40.0-7.redhat_00015.1.el8eap
    • 0:2.3.24-3.SP2_redhat_00001.1.el8eap
    • 0:8.1.6-7.GA_redhat_00010.1.el8eap
    • 0:801.6.1-1.GA_redhat_00001.1.el8eap
    Red HatRed Hat JBoss Enterprise Application Platform 8.1 for RHEL 9
    • < 0:801.6.1-1.GA_redhat_00001.1.el9eap
    • < 0:2.3.24-3.SP2_redhat_00001.1.el9eap
    • < 0:8.1.6-7.GA_redhat_00010.1.el9eap
    • < 0:2.40.0-7.redhat_00015.1.el9eap
    • 0:801.6.1-1.GA_redhat_00001.1.el9eap
    • 0:2.3.24-3.SP2_redhat_00001.1.el9eap
    • 0:8.1.6-7.GA_redhat_00010.1.el9eap
    • 0:2.40.0-7.redhat_00015.1.el9eap
    Red HatRed Hat JBoss Enterprise Application Platform 8.1.6
    • < 2.3.24.SP2-redhat-00001
    • 2.3.24.SP2-redhat-00001
    Red HatRed Hat JBoss Enterprise Application Platform Expansion Pack
    • —
    • —
    Red HatRed Hat Process Automation 7
    • —
    • —
    Red HatRed Hat Single Sign-On 7
    • —
    • —
    redhatbuild_of_apache_camel_-_hawtio
    • 4.0
    • —
    redhatbuild_of_apache_camel_for_spring_boot
    • 4.0
    • —
    redhatdata_grid
    • 8.0
    • —
    redhatfuse
    • 7.0.0
    • —
    redhatjboss_enterprise_application_platform
    • 8.0.0
    • 7.0.0
    • —
    • —
    redhatjboss_enterprise_application_platform_expansion_pack
    • —
    • —
    redhatprocess_automation
    • 7.0
    • —
    redhatsingle_sign-on
    • 7.0
    • —
    redhatundertow
    • —
    • —
    OracleCommunications
    • 7.5.0
    • 15.0.1.0.0
    • 26.1.202
    • 7.7.0
    • 25.1.100
    • 47.0.0.2.0
    • 7.0.0
    • 6
    • 6.1
    • 7.8.0
    • 24.2.4-25.2.000
    • 7.5.1
    • 25.2.100
    • 8.0-8.1
    • 8.0.1
    • 7.6.0
    • 14
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —

    Affected operating systems

    Affected operating systems
    FamilyVendorProductVersion
    Linuxredhatenterprise_linux9.0

    Weakness classes (CWE)

    • CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

      Base

      The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

      Entry at MITRE CWE-444

    References & sources

    Reanalysis & status changes

    Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.

    1. CVE Modifiedsecalert@redhat.com

      • Affected: after Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/28xxx/CVE-2026-28369.json">CVE-2026-28369</a>

    2. CVE Modifiedsecalert@redhat.com

      • Affected: after Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/28xxx/CVE-2026-28369.json">CVE-2026-28369</a>
      • Reference: after https://access.redhat.com/errata/RHSA-2026:25125
      • Reference: after https://access.redhat.com/errata/RHSA-2026:25126
      • Reference: after https://access.redhat.com/security/cve/CVE-2026-28369

    3. CVE Modifiedsecalert@redhat.com

      • Affected: before Red Hat JBoss Enterprise Application Platform 8.1, Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8, Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (+21) after Red Hat JBoss Enterprise Application Platform 8.1, Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8, Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 (+21)

    4. CVE Modifiedsecalert@redhat.com

      • Reference: after https://access.redhat.com/errata/RHSA-2026:25125
      • Reference: after https://access.redhat.com/errata/RHSA-2026:25126
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