HighCVE-2026-53183

    Linux Kernel: security vulnerability (CVE-2026-53183)

    Published Last modified Sources: SUSE, Debian LTS, Ubuntu, BSI, Siemens ProductCERT, CVE.org, Msrc Update Guide

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: mptcp: allow subflow rcv wnd to shrink In MPTCP connection, the `window` field in the TCP header refers to the MPTCP-level rcv_nxt and it's right edge should not move backward. Such constraint is enforced at DSS option generation time.

    Update Linux Kernel to version 6.1.176, Linux Kernel to version 6.6.143, Linux Kernel to version 6.12.94.

    Affected
    • Linux Kernel lt 5.19..6.1.176
    • Linux Kernel lt 6.2..6.6.143
    • Linux Kernel lt 6.7..6.12.94
    • Linux Kernel lt 6.13..6.18.36
    • Linux Kernel lt 6.19..7.0.13
    Fixed in
    • Linux Kernel 6.1.176
    • Linux Kernel 6.6.143
    • Linux Kernel 6.12.94
    • Linux Kernel 6.18.36
    • Linux Kernel 7.0.13
    • Linux Kernel 7.1

    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: Vendor (CNA), CVSS v3

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: SUSE, Debian LTS, Ubuntu, BSI, Siemens ProductCERT, CVE.org, Msrc Update Guide

    0.5 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 42.1

    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
    71.13 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
    0.5 %
    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
    42.1
    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: partial
    Source: CISA Vulnrichment, as of 16 October 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-400

    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

    In the Linux kernel, the following vulnerability has been resolved: mptcp: allow subflow rcv wnd to shrink In MPTCP connection, the `window` field in the TCP header refers to the MPTCP-level rcv_nxt and it's right edge should not move backward. Such constraint is enforced at DSS option generation time. At the same time, the TCP stack ensures independently that the TCP-level rcv wnd right's edge does not move backward. That in turn causes artificial inflating of the MPTCP rcv window when the incoming data is acked at the TCP level and is OoO in the MPTCP sequence space (or lands in the backlog). As a consequence, the incoming traffic can exceed the receiver rcvbuf size even when the sender is not misbehaving. Prevent such scenario forcibly allowing the TCP subflow to shrink the TCP-level rcv wnd regardless of the current netns setting.

    Source: suse_csaf, Debian LTS Advisories, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, siemens_advisory, cvelistv5, NVD (NIST), Microsoft Security Update Guide, CVE.org (MITRE)

    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
    LinuxLinux
    • 6.7 – < 6.12.94
    • 6.13 – < 6.18.36
    • 5.19 – < 6.1.176
    • —
    • 6.19 – < 7.0.13
    • 6.2 – < 6.6.143
    • 6.12.94
    • 6.18.36
    • 6.1.176
    • 7.1
    • 7.0.13
    • 6.6.143
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel7.1
    Linuxlinuxlinux_kernel—

    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

    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 modifiedCISA ADP

      Weakness type: CWE-400

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-400

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

    2. Record modifiedCISA ADP

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

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-53183","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:26:14.847841Z"}

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

    3. Record modifiedLinux

      Show 18 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/653245266913f03fcf21cbca68eed5c197a33e52
      Referenceadded
      —
      https://git.kernel.org/stable/c/aa3861f40ac32706d9e97bfac76984613e278788
      Referenceadded
      —
      https://git.kernel.org/stable/c/b1fd13074f22105deec45aa02283e322733e0c2d
      Referenceadded
      —
      https://git.kernel.org/stable/c/bf364b0f10b27679140699821f88af7f01e2a6e3
      Referenceadded
      —
      https://git.kernel.org/stable/c/c297a4e65c50a2b807d9309b22615080faffa8f3
      Referenceadded
      —
      https://git.kernel.org/stable/c/da23be77e1292cd611e736c3aa17da633d7ddce7
      Referenceremoved
      https://git.kernel.org/stable/c/653245266913f03fcf21cbca68eed5c197a33e52
      —
      Referenceremoved
      https://git.kernel.org/stable/c/aa3861f40ac32706d9e97bfac76984613e278788
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b1fd13074f22105deec45aa02283e322733e0c2d
      —
      Referenceremoved
      https://git.kernel.org/stable/c/bf364b0f10b27679140699821f88af7f01e2a6e3
      —
      Referenceremoved
      https://git.kernel.org/stable/c/c297a4e65c50a2b807d9309b22615080faffa8f3
      —
      Referenceremoved
      https://git.kernel.org/stable/c/da23be77e1292cd611e736c3aa17da633d7ddce7
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/653245266913f03fcf21cbca68eed5c197a33e52 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/aa3861f40ac32706d9e97bfac76984613e278788 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b1fd13074f22105deec45aa02283e322733e0c2d Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/bf364b0f10b27679140699821f88af7f01e2a6e3 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/c297a4e65c50a2b807d9309b22615080faffa8f3 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/da23be77e1292cd611e736c3aa17da633d7ddce7 Types: Patch
      —

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    4. Record modifiedSiemens ADP

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/53xxx/CVE-2026-53183.json">CVE-2026-53183</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

      Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

    5. Initial analysis by NVDNVD

      Newly listed as affected:
      • Linux Kernel (6.2 – before 6.6.143; 6.13 – before 6.18.36; 6.7 – before 6.12.94; 5.19 – before 6.1.176; 6.19 – before 7.0.13; 6 individual versions)
      Show 8 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      NVD-CWE-noinfo
      Product configurationadded
      —
      OR *cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.2 up to (excluding) 6.6.143 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.18.36 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.12.94 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.19 up to (excluding) 6.1.176 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.13 *cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc6:*:*:*:*:*:*
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/653245266913f03fcf21cbca68eed5c197a33e52 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/aa3861f40ac32706d9e97bfac76984613e278788 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/b1fd13074f22105deec45aa02283e322733e0c2d Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/bf364b0f10b27679140699821f88af7f01e2a6e3 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/c297a4e65c50a2b807d9309b22615080faffa8f3 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/da23be77e1292cd611e736c3aa17da633d7ddce7 Types: Patch

      Source identifier: nvd@nist.gov

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