HighCVE-2026-46107

    Linux Kernel: security vulnerability (CVE-2026-46107)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: dm-thin: fix metadata refcount underflow There's a bug in dm-thin in the function rebalance_children. If the internal btree node has one entry, the code tries to copy all btree entries from the node's child to the node itself and then decrement the child's reference count.

    Update Linux Kernel to version 5.10.259, Linux Kernel to version 5.15.209, Linux Kernel to version 6.1.175.

    Affected
    • Linux Kernel lt 3.2..5.10.259
    • 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..6.12.88
    • Linux Kernel lt 6.13..6.18.30
    • Linux Kernel lt 6.19..7.0.7
    Fixed in
    • Linux Kernel 5.10.259
    • Linux Kernel 5.15.209
    • Linux Kernel 6.1.175
    • Linux Kernel 6.6.140
    • Linux Kernel 6.12.88
    • Linux Kernel 6.18.30
    • Linux Kernel 7.0.7
    • Linux Kernel 7.1

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

    Metrics

    7.8

    Priority

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

    Source: Vendor (CNA), CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: SUSE, 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 0.9

    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
    57.06 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
    7.8 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
    7.8
    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“.

    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
    0.9
    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
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: total
    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-667

    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: dm-thin: fix metadata refcount underflow There's a bug in dm-thin in the function rebalance_children. If the internal btree node has one entry, the code tries to copy all btree entries from the node's child to the node itself and then decrement the child's reference count. If the child node is shared (it has reference count > 1), we won't free it, so there would be two pointers to each of the grandchildren nodes. But the reference counts of the grandchildren is not increased, thus the reference count doesn't match the number of pointers that point to the grandchildren. This results in "device mapper: space map common: unable to decrement block" errors. Fix this bug by incrementing reference counts on the grandchildren if the btree node is shared.

    Source: suse_csaf, 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
    • 6.7 – < 6.12.88
    • 6.2 – < 6.6.140
    • 3.2 – < 5.10.259
    • 6.19 – < 7.0.7
    • 5.11 – < 5.15.209
    • —
    • 6.13 – < 6.18.30
    • 6.1.175
    • 6.12.88
    • 6.6.140
    • 5.10.259
    • 7.0.7
    • 5.15.209
    • 7.1
    • 6.18.30
    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_kernel7.1
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-667Improper Locking

      Class

      The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

      Entry at MITRE CWE-667

    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-667

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-667

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

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-46107","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:19:39.761599Z"}

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

    3. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/09a65adc7d8bbfce06392cb6d375468e2728ead5
      Referenceadded
      —
      https://git.kernel.org/stable/c/12161e03d33afce781f68fa11cc6060538862fad
      Referenceadded
      —
      https://git.kernel.org/stable/c/323d252a4a378834e4fe68298ca61cfc5dd3a460
      Referenceadded
      —
      https://git.kernel.org/stable/c/5ec0debbcfd43596e32c1239e993de06a704e04c
      Referenceadded
      —
      https://git.kernel.org/stable/c/85311a585a26640760cd0f3349ab9f2905691044
      Referenceadded
      —
      https://git.kernel.org/stable/c/b719d12cb94df345e9ad2715fd0abe9afcaeb111
      Referenceadded
      —
      https://git.kernel.org/stable/c/f06f6aededd792a754cd677c02b3d3016d868c2c
      Referenceadded
      —
      https://git.kernel.org/stable/c/f49b41c9eb7c6ff00df27cd49cea210abbadd8ad
      Referenceremoved
      https://git.kernel.org/stable/c/09a65adc7d8bbfce06392cb6d375468e2728ead5
      —
      Referenceremoved
      https://git.kernel.org/stable/c/12161e03d33afce781f68fa11cc6060538862fad
      —
      Referenceremoved
      https://git.kernel.org/stable/c/323d252a4a378834e4fe68298ca61cfc5dd3a460
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5ec0debbcfd43596e32c1239e993de06a704e04c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/85311a585a26640760cd0f3349ab9f2905691044
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b719d12cb94df345e9ad2715fd0abe9afcaeb111
      —
      Referenceremoved
      https://git.kernel.org/stable/c/f06f6aededd792a754cd677c02b3d3016d868c2c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/f49b41c9eb7c6ff00df27cd49cea210abbadd8ad
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/09a65adc7d8bbfce06392cb6d375468e2728ead5 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/12161e03d33afce781f68fa11cc6060538862fad Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/323d252a4a378834e4fe68298ca61cfc5dd3a460 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/5ec0debbcfd43596e32c1239e993de06a704e04c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/85311a585a26640760cd0f3349ab9f2905691044 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b719d12cb94df345e9ad2715fd0abe9afcaeb111 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/f06f6aededd792a754cd677c02b3d3016d868c2c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/f49b41c9eb7c6ff00df27cd49cea210abbadd8ad 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/2026/46xxx/CVE-2026-46107.json">CVE-2026-46107</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

    5. Record modifiedLinux

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/b719d12cb94df345e9ad2715fd0abe9afcaeb111
      Affected versions (publisher)changed
      Linux, Linux
      Linux, Linux

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

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