MediumCVE-2026-46040

    Linux Kernel: security vulnerability (CVE-2026-46040)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: inotify: fix watch count leak when fsnotify_add_inode_mark_locked() fails When fsnotify_add_inode_mark_locked() fails in inotify_new_watch(), the error path calls inotify_remove_from_idr() but does not call dec_inotify_watches() to undo the preceding inc_inotify_watches(). This leaks a watch count, and repeated failures can exhaust the max_user_watches limit with -ENOSPC even when no watches are active.

    Update Linux Kernel to version 5.10.258, Linux Kernel to version 5.15.209, Linux Kernel to version 6.1.175.

    Affected
    • Linux Kernel lt 4.11..5.10.258
    • Linux Kernel lt 5.11..5.15.209
    • Linux Kernel lt 5.16..6.1.175
    • Linux Kernel lt 6.2..6.6.140
    • Linux Kernel lt 6.7..6.12.86
    • Linux Kernel lt 6.13..6.18.27
    • Linux Kernel lt 6.19..7.0.4
    Fixed in
    • Linux Kernel 5.10.258
    • Linux Kernel 5.15.209
    • Linux Kernel 6.1.175
    • Linux Kernel 6.6.140
    • Linux Kernel 6.12.86
    • Linux Kernel 6.18.27
    • Linux Kernel 7.0.4
    • Linux Kernel 7.1

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

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.5

    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
    45.43 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
    2.5
    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: inotify: fix watch count leak when fsnotify_add_inode_mark_locked() fails When fsnotify_add_inode_mark_locked() fails in inotify_new_watch(), the error path calls inotify_remove_from_idr() but does not call dec_inotify_watches() to undo the preceding inc_inotify_watches(). This leaks a watch count, and repeated failures can exhaust the max_user_watches limit with -ENOSPC even when no watches are active. Prior to commit 1cce1eea0aff ("inotify: Convert to using per-namespace limits"), the watch count was incremented after fsnotify_add_mark_locked() succeeded, so this path was not affected. The conversion moved inc_inotify_watches() before the mark insertion without adding the corresponding rollback. Add the missing dec_inotify_watches() call in the error path.

    Source: suse_csaf, siemens_advisory, Debian LTS Advisories, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, cvelistv5, Microsoft Security Update Guide, ENISA EUVD, NVD (NIST), 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
    • 6.19 – < 7.0.4
    • 6.2 – < 6.6.140
    • 4.11 – < 5.10.258
    • 6.13 – < 6.18.27
    • 5.11 – < 5.15.209
    • —
    • 6.7 – < 6.12.86
    • 6.1.175
    • 7.0.4
    • 6.6.140
    • 5.10.258
    • 6.18.27
    • 5.15.209
    • 7.1
    • 6.12.86
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    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 modifiedSiemens ADP

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/46xxx/CVE-2026-46040.json">CVE-2026-46040</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

    2. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/10edf7e0ffdc7faa18e2244b17722c1b882b8273
      Referenceadded
      —
      https://git.kernel.org/stable/c/3ab58cf42c46bf2366d2f55ae5c59299d5e178b7
      Referenceadded
      —
      https://git.kernel.org/stable/c/3ad9ccea1b25435f6179b57aa891960beb7ce8f9
      Referenceadded
      —
      https://git.kernel.org/stable/c/6a320935fa4293e9e599ec9f85dc9eb3be7029f8
      Referenceadded
      —
      https://git.kernel.org/stable/c/73ddc8518a32baff6bc17afda4ee1ebae5b4ed12
      Referenceadded
      —
      https://git.kernel.org/stable/c/8bcc1cd237ab5ccfdd102869fa031c541943cf40
      Referenceadded
      —
      https://git.kernel.org/stable/c/9e48844f708eb48bae4e79cb21edc097c966306d
      Referenceadded
      —
      https://git.kernel.org/stable/c/fdaa42ca370d056428e5e171247c8fdce8dff36a
      Referenceremoved
      https://git.kernel.org/stable/c/10edf7e0ffdc7faa18e2244b17722c1b882b8273
      —
      Referenceremoved
      https://git.kernel.org/stable/c/3ab58cf42c46bf2366d2f55ae5c59299d5e178b7
      —
      Referenceremoved
      https://git.kernel.org/stable/c/3ad9ccea1b25435f6179b57aa891960beb7ce8f9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/6a320935fa4293e9e599ec9f85dc9eb3be7029f8
      —
      Referenceremoved
      https://git.kernel.org/stable/c/73ddc8518a32baff6bc17afda4ee1ebae5b4ed12
      —
      Referenceremoved
      https://git.kernel.org/stable/c/8bcc1cd237ab5ccfdd102869fa031c541943cf40
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9e48844f708eb48bae4e79cb21edc097c966306d
      —
      Referenceremoved
      https://git.kernel.org/stable/c/fdaa42ca370d056428e5e171247c8fdce8dff36a
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/10edf7e0ffdc7faa18e2244b17722c1b882b8273 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/3ab58cf42c46bf2366d2f55ae5c59299d5e178b7 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/3ad9ccea1b25435f6179b57aa891960beb7ce8f9 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/6a320935fa4293e9e599ec9f85dc9eb3be7029f8 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/73ddc8518a32baff6bc17afda4ee1ebae5b4ed12 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8bcc1cd237ab5ccfdd102869fa031c541943cf40 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/9e48844f708eb48bae4e79cb21edc097c966306d Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/fdaa42ca370d056428e5e171247c8fdce8dff36a Types: Patch
      —

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

    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/2026/46xxx/CVE-2026-46040.json">CVE-2026-46040</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html

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

    4. Initial analysis by NVDNVD

      Newly listed as affected:
      • Linux Kernel (6.7 – before 6.12.86; 5.16 – before 6.1.175; 5.11 – before 5.15.209; 6.2 – before 6.6.140; 6.13 – before 6.18.27; 6.19 – before 7.0.4; 4.11 – before 5.10.258)

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

      Show 11 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
      Weakness type (CWE)added
      —
      NVD-CWE-Other
      Product configurationadded
      —
      OR *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.12.86 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.16 up to (excluding) 6.1.175 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.11 up to (excluding) 5.15.209 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.2 up to (excluding) 6.6.140 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.18.27 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.4 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 4.11 up to (excluding) 5.10.258
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/10edf7e0ffdc7faa18e2244b17722c1b882b8273 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/3ab58cf42c46bf2366d2f55ae5c59299d5e178b7 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/3ad9ccea1b25435f6179b57aa891960beb7ce8f9 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/6a320935fa4293e9e599ec9f85dc9eb3be7029f8 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/73ddc8518a32baff6bc17afda4ee1ebae5b4ed12 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/8bcc1cd237ab5ccfdd102869fa031c541943cf40 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/9e48844f708eb48bae4e79cb21edc097c966306d Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/fdaa42ca370d056428e5e171247c8fdce8dff36a Types: Patch

      Source identifier: nvd@nist.gov

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