CriticalCVE-2026-65637

    Apache Tomcat: HTTP/2 no-authority bypass of strict SNI validation - CVE-2026-32990 fix incomplete (CVE-2026-65637)

    Published Last modified Sources: Red Hat, OSV, CVE.org, SUSE, BSI

    What is affected, what to do

    A flaw was found in Apache Tomcat. This improper input validation vulnerability, stemming from an incomplete fix for CVE-2026-32990, allows for an HTTP/2 no-authority bypass of strict Server Name Indication (SNI) validation.

    Update tomcat to version 11.0.25, Tomcat to version 10.1.57, org.apache.tomcat.embed:tomcat-embed-core to version 11.0.25.

    Affected
    • Apache Tomcat lte 11.0.20..11.0.24
    • Apache Tomcat lte 10.1.53..10.1.57
    • Apache Tomcat lte 9.0.115..9.0.120

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

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

    Source: Vendor (CNA), CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: Red Hat, OSV, CVE.org, SUSE, BSI

    0.6 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 49.2

    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
    92.75 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
    9.8 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
    9.8
    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“.

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    0.6 %
    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.

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    49.2
    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
    CISA assessment (SSVC)
    Exploitation: none known · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 26 August 2026
    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-20

    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 Apache Tomcat. This improper input validation vulnerability, stemming from an incomplete fix for CVE-2026-32990, allows for an HTTP/2 no-authority bypass of strict Server Name Indication (SNI) validation. This could potentially lead to unauthorized access or misrouting of requests.

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

    Affected products

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

    Affected products
    Affected versionsFixed in
    Apache Software FoundationApache Tomcat
    • 9.0.115 – ≤ 9.0.120
    • 10.1.53 – ≤ 10.1.57
    • 11.0.20 – ≤ 11.0.24
    • —
    • —
    • —
    apachetomcat
    • 11.0.20 – < 11.0.25
    • 9.0.115 – < 9.0.121
    • 10.1.53 – < 10.1.58
    • 11.0.25
    • 9.0.121
    • 10.1.58
    ApacheTomcat
    • < 10.1.57
    • < 11.0.25
    • < 9.0.121
    • 10.1.57
    • 11.0.25
    • 9.0.121
    mavenorg.apache.tomcat.embed:tomcat-embed-core
    • 11.0.21
    • 9.0.118
    • 10.1.55
    • 9.0.117
    • 9.0.119
    • 11.0.24
    • 11.0.20
    • 11.0.22
    • 9.0.116
    • 10.1.54
    • 10.1.57
    • 10.1.56
    • 11.0.23
    • 9.0.115
    • 9.0.120
    • 10.1.53
    • —
    • —
    • —
    • —
    • —
    • —
    • 11.0.25
    • —
    • —
    • —
    • —
    • —
    • —
    • 9.0.121
    • —
    • 10.1.59
    mavenorg.apache.tomcat:tomcat-coyote
    • 10.1.53
    • 9.0.118
    • 9.0.119
    • 9.0.116
    • 9.0.120
    • 9.0.115
    • 10.1.57
    • 11.0.24
    • 9.0.117
    • 11.0.22
    • 11.0.21
    • 11.0.20
    • 11.0.23
    • 10.1.56
    • 10.1.55
    • 10.1.54
    • 10.1.59
    • —
    • —
    • —
    • —
    • 9.0.121
    • —
    • —
    • —
    • —
    • —
    • 11.0.25
    • —
    • —
    • —
    • —
    Distribution and container packages (3)

    Downstream packages (e.g. Bitnami, Debian, Ubuntu, Red Hat). Versions refer to the distribution, not the vendor.

    Distribution and container packages
    Affected versionsFixed in
    bitnamitomcat
    • 11.0.20
    • 9.0.115
    • 10.1.53
    • 11.0.25
    • 9.0.121
    • 10.1.58

    Vendors and products

    Weakness classes (CWE)

    • CWE-20Improper Input Validation

      Class

      The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

      Entry at MITRE CWE-20

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Initial analysis by NVDNVD

      Newly listed as affected:
      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:* versions from (including) 10.1.53 up to (excluding) 10.1.58 *cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:* versions from (including) 11.0.20 up to (excluding) 11.0.25 *cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:* versions from (including) 9.0.115 up to (excluding) 9.0.121
      Reference typeadded
      —
      Apache Software Foundation: https://lists.apache.org/thread/djog953z1ohsyt25bdvhfzbmsy22vgcj Types: Mailing List, Vendor Advisory

      Source identifier: nvd@nist.gov

    2. Record modifiedApache

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://lists.apache.org/thread/djog953z1ohsyt25bdvhfzbmsy22vgcj
      Referenceremoved
      https://lists.apache.org/thread/djog953z1ohsyt25bdvhfzbmsy22vgcj
      —

      Source identifier: security@apache.org

    3. Record modifiedCISA ADP

      CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

      CISA assessment (SSVC): exploitation: none known, automatable: yes

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
      SSVC assessmentadded
      —
      {"id":"CVE-2026-65637","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-26T15:20:15.521688Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    4. ReceivedApache

      Weakness type: CWE-20

      Description added or changed

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Apache Tomcat
      Descriptionadded
      —
      Improper Input Validation vulnerability in Apache Tomcat due to incomplete fix for CVE-2026-32990. This issue affects Apache Tomcat: from 11.0.20 through 11.0.24, from 10.1.53 through 10.1.57, from 9.0.115 through 9.0.120. Users are recommended to upgrade to version 11.0.25, 10.1.58 or 9.0.121, which fix the issue.
      Weakness type (CWE)added
      —
      CWE-20
      Referenceadded
      —
      https://lists.apache.org/thread/djog953z1ohsyt25bdvhfzbmsy22vgcj

      Source identifier: security@apache.org

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