MediumCVE-2026-31617

    Linux Kernel: security vulnerability (CVE-2026-31617)

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

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    What is affected, what to do

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Conflicting version data — version display is hidden until the data is resolved.

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    Metrics

    5.5

    Priority

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

    Source: NVD, CVSS v3

    5.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.9

    Show all metrics
    Severity
    Medium
    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
    44.00 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
    5.5 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
    5.5
    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
    0.1 %
    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
    2.9
    Low — this CVE sits in the lower 10% of all CVEs scored today.
    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

    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
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    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:

    usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()

    The block_len read from the host-supplied NTB header is checked against ntb_max but has no lower bound. When block_len is smaller than opts->ndp_size, the bounds check of: ndp_index > (block_len - opts->ndp_size) will underflow producing a huge unsigned value that ndp_index can never exceed, defeating the check entirely.

    The same underflow occurs in the datagram index checks against block_len

    • opts->dpe_size. With those checks neutered, a malicious USB host can choose ndp_index and datagram offsets that point past the actual transfer, and the skb_put_data() copies adjacent kernel memory into the network skb.

    Fix this by rejecting block lengths that cannot hold at least the NTB header plus one NDP. This will make block_len - opts->ndp_size and block_len - opts->dpe_size both well-defined.

    Commit 8d2b1a1ec9f5 ("CDC-NCM: avoid overflow in sanity checking") fixed a related class of issues on the host side of NCM.

    Source: suse_csaf, Debian Security Advisories, Debian LTS Advisories, Ubuntu Security Notices, siemens_advisory, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), Microsoft Security Update Guide, ENISA EUVD, 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
    • 5.16 – < 6.1.175
    • 5.9 – < 5.10.258
    • 5.4.62 – < 5.5
    • 6.2 – < 6.6.136
    • 4.14.196 – < 4.15
    • 6.19 – < 6.19.14
    • 4.19.143 – < 4.20
    • 5.8.6 – < 5.9
    • 5.11 – < 5.15.209
    • 4.9.235 – < 4.10
    • 6.13 – < 6.18.24
    • —
    • 6.7 – < 6.12.83
    • 6.20 – < 7.0.1
    • 6.1.175
    • 5.10.258
    • 5.5
    • 6.6.136
    • 4.15
    • 6.19.14
    • 4.20
    • 5.9
    • 5.15.209
    • 4.10
    • 6.18.24
    • 7.1
    • 6.12.83
    • 7.0.1
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinuxtrixie
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel—

    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 modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
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      https://git.kernel.org/stable/c/068a7f2749fff6462a0a908ec415b885fe430f50
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      https://git.kernel.org/stable/c/0f156bb5334e588034ca68ac2ee92b23f66e56e7
      Referenceadded
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      https://git.kernel.org/stable/c/1425655c2870054c3ab4712e2b6dbdd331597ada
      Referenceadded
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      https://git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135
      Referenceadded
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      https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126
      Referenceadded
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      https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1
      Referenceadded
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      https://git.kernel.org/stable/c/8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca
      Referenceadded
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      https://git.kernel.org/stable/c/8f993d30b95dc9557a8a96ceca11abed674c8acb
      Referenceadded
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      https://git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7
      Referenceremoved
      https://git.kernel.org/stable/c/068a7f2749fff6462a0a908ec415b885fe430f50
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      Referenceremoved
      https://git.kernel.org/stable/c/0f156bb5334e588034ca68ac2ee92b23f66e56e7
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      Referenceremoved
      https://git.kernel.org/stable/c/1425655c2870054c3ab4712e2b6dbdd331597ada
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      Referenceremoved
      https://git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135
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      Referenceremoved
      https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126
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      Referenceremoved
      https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1
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      Referenceremoved
      https://git.kernel.org/stable/c/8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca
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      Referenceremoved
      https://git.kernel.org/stable/c/8f993d30b95dc9557a8a96ceca11abed674c8acb
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/0f156bb5334e588034ca68ac2ee92b23f66e56e7 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8f993d30b95dc9557a8a96ceca11abed674c8acb Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7 Types: Patch
      —

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

    2. Record modifiedRed Hat ADP

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://access.redhat.com/security/cve/CVE-2026-31617
      Referenceadded
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      https://bugzilla.redhat.com/show_bug.cgi?id=2461448
      Referenceadded
      —
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31617.json
      Referenceremoved
      https://access.redhat.com/security/cve/CVE-2026-31617
      —
      Referenceremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2461448
      —
      Referenceremoved
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31617.json
      —

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

    3. 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/2026/31xxx/CVE-2026-31617.json">CVE-2026-31617</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

    4. Record modifiedRed Hat ADP

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

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

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
      CVSSremoved
      AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
      —

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

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