HighCVE-2026-12151

    undici WebSocket client vulnerable to denial of service via fragment count bypass (CVE-2026-12151)

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

    What is affected, what to do

    A flaw was found in undici. A malicious WebSocket server can exploit this by streaming numerous small or empty continuation frames.

    Update Undici to version 6.26.0, Undici to version 7.28.0, Undici to version 8.5.0.

    Affected
    • Undici lt *..6.26.0
    • Undici lt 7.0.0..7.28.0
    • Undici lt 8.0.0..8.5.0
    Fixed in
    • Undici 6.26.0
    • Undici 7.28.0
    • Undici 8.5.0

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

    Metrics

    7.5

    Priority

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

    Source: NVD, CVSS v3

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

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

    0.8 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 56.0

    Show all metrics
    Severity
    High
    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
    81.77 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
    7.5 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
    7.5
    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
    0.8 %
    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
    56.0
    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-400, CWE-770

    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 undici. A malicious WebSocket server can exploit this by streaming numerous small or empty continuation frames. This can bypass per-frame and cumulative-size validation, leading to unbounded memory growth in the client process. The primary consequence is memory exhaustion, resulting in a denial of service (DoS) for affected applications using the undici WebSocket client or WebSocketStream API.

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

    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
    undiciundici
    • 7.0.0 – < 7.28.0
    • < 6.26.0
    • 8.0.0 – < 8.5.0
    • 7.28.0
    • 6.26.0
    • 8.5.0
    nodejsundici
    • 6.17.0 – < 6.27.0
    • 7.0.0 – < 7.28.0
    • 8.0.0 – < 8.5.0
    • 6.27.0
    • 7.28.0
    • 8.5.0
    IBMApp Connect Enterprise
    • < 12.0.12.28
    • < 13.0.8.1
    • 12.0.12.28
    • 13.0.8.1
    IBMApp Connect Enterprise CD
    • < 13.4.0
    • 13.4.0
    IBMApp Connect Enterprise LTS
    • < 13.4.0
    • < 12.0.26
    • 13.4.0
    • 12.0.26
    npmundici
    • 8.0.0
    • —
    • 7.0.0
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-400Uncontrolled Resource Consumption

      Class

      The product does not properly control the allocation and maintenance of a limited resource.

      Entry at MITRE CWE-400
    • CWE-770Allocation of Resources Without Limits or Throttling

      Base

      The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

      Entry at MITRE CWE-770

    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. Record modifiedRed Hat ADP

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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:66488
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      https://access.redhat.com/errata/RHSA-2026:66545

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    2. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    3. Record modifiedRed Hat ADP

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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:65126

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    4. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    5. Record modifiedOpenJS Foundation

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      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
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      https://cna.openjsf.org/security-advisories.html
      Referenceadded
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      https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q
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      https://cna.openjsf.org/security-advisories.html
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      https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q
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      Reference typeremoved
      https://cna.openjsf.org/security-advisories.html Types: Vendor Advisory
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      Reference typeremoved
      https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q Types: Vendor Advisory
      —

      Source identifier: ce714d77-add3-4f53-aff5-83d477b104bb

    Show 13 older changes
    1. Record modifiedRed Hat ADP

      Show 50 original changes
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      https://access.redhat.com/errata/RHSA-2026:34342
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      https://access.redhat.com/errata/RHSA-2026:35841
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      https://access.redhat.com/errata/RHSA-2026:36820
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      https://access.redhat.com/errata/RHSA-2026:38009
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      https://access.redhat.com/errata/RHSA-2026:38236
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      https://access.redhat.com/errata/RHSA-2026:39246
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      https://access.redhat.com/errata/RHSA-2026:39868
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      https://access.redhat.com/errata/RHSA-2026:41929
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      https://access.redhat.com/errata/RHSA-2026:41947
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      https://access.redhat.com/errata/RHSA-2026:47728
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      https://access.redhat.com/errata/RHSA-2026:48151
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      https://access.redhat.com/errata/RHSA-2026:52399
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      https://access.redhat.com/errata/RHSA-2026:56366
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      https://access.redhat.com/errata/RHSA-2026:60520
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      https://access.redhat.com/security/cve/CVE-2026-12151
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      https://bugzilla.redhat.com/show_bug.cgi?id=2489980
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      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12151.json
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      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    2. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

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      TypeActionBeforeAfter
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      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+111)
      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+111)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    3. Record modifiedRed Hat ADP

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      https://access.redhat.com/errata/RHSA-2026:57013
      Affected versions (publisher)changed
      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+89)
      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+111)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    4. Record modifiedRed Hat ADP

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      https://access.redhat.com/errata/RHSA-2026:56366
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      https://access.redhat.com/errata/RHSA-2026:56431
      Affected versions (publisher)changed
      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+53)
      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+89)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    5. Record modifiedRed Hat ADP

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      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    6. Record modifiedRed Hat ADP

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      https://access.redhat.com/errata/RHSA-2026:47728
      Affected versions (publisher)changed
      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+51)
      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+52)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    7. Record modifiedRed Hat ADP

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      https://access.redhat.com/errata/RHSA-2026:48124
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      https://access.redhat.com/errata/RHSA-2026:48151
      Affected versions (publisher)changed
      Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support (+51)
      Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+51)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    8. Record modifiedRed Hat ADP

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      https://access.redhat.com/errata/RHSA-2026:41947
      Affected versions (publisher)changed
      Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support (+50)
      Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support (+51)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    9. Record modifiedRed Hat ADP

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      https://access.redhat.com/errata/RHSA-2026:36820
      Affected versions (publisher)changed
      Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 9), Cluster Observability Operator 1.5.0 (+12)
      Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 9), Cluster Observability Operator 1.5.0 (+13)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    10. Record modifiedRed Hat ADP

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      https://access.redhat.com/errata/RHSA-2026:35842
      Affected versions (publisher)changed
      Cluster Observability Operator 1.5.0, Cryostat 4, OpenShift Pipelines (+12)
      Red Hat Enterprise Linux AppStream (v. 10), Cluster Observability Operator 1.5.0, Cryostat 4 (+12)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    11. Initial analysis by NVDNVD

      Newly listed as affected:
      • Nodejs undici (8.0.0 – before 8.5.0; 7.0.0 – before 7.28.0; 6.17.0 – before 6.27.0)
      Show 3 original changes
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      Product configurationadded
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      OR *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 8.0.0 up to (excluding) 8.5.0 *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 7.0.0 up to (excluding) 7.28.0 *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 6.17.0 up to (excluding) 6.27.0
      Reference typeadded
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      openjs: https://cna.openjsf.org/security-advisories.html Types: Vendor Advisory
      Reference typeadded
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      openjs: https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q Types: Vendor Advisory

      Source identifier: nvd@nist.gov

    12. Record modifiedCISA ADP

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

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      {"id":"CVE-2026-12151","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-06-17T17:29:57.305732Z"}

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

    13. ReceivedOpenJS Foundation

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

      Weakness type: CWE-400, CWE-770

      Description added or changed

      Show 7 original changes
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      TypeActionBeforeAfter
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      undici
      Descriptionadded
      —
      Impact: The undici WebSocket client enforces maxPayloadSize on the cumulative byte count of fragments in a message but does not enforce a limit on the number of fragments. A malicious WebSocket server can stream many small or empty continuation frames that each pass per-frame and cumulative-size validation, collectively causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service. Affected applications are those using the undici WebSocket client (new WebSocket(...)) or the WebSocketStream API that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint. All releases starting at undici 6.17.0 are affected. Patches: Upgrade to undici >= 6.26.0, >= 7.28.0, or >= 8.5.0. Workarounds: No workaround is available. The fix must be applied through an upgrade.
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
      Weakness type (CWE)added
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      CWE-400
      Weakness type (CWE)added
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      CWE-770
      Referenceadded
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      https://cna.openjsf.org/security-advisories.html
      Referenceadded
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      https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q

      Source identifier: ce714d77-add3-4f53-aff5-83d477b104bb

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