MediumCVE-2025-21846

    Linux Kernel: security vulnerability (CVE-2025-21846)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: acct: perform last write from workqueue In [1] it was reported that the acct(2) system call can be used to trigger NULL deref in cases where it is set to write to a file that triggers an internal lookup. This can e.g., happen when pointing acc(2) to /sys/power/resume.

    Update Linux Kernel to version 5.4.291, Linux Kernel to version 5.10.235, Linux Kernel to version 5.15.179.

    Affected
    • Linux Kernel lt 2.6.12..5.4.291
    • Linux Kernel lt 5.5..5.10.235
    • Linux Kernel lt 5.11..5.15.179
    • Linux Kernel lt 5.16..6.1.130
    • Linux Kernel lt 6.2..6.6.80
    • Linux Kernel lt 6.7..6.12.17
    • Linux Kernel lt 6.13..6.13.5
    Fixed in
    • Linux Kernel 5.4.291
    • Linux Kernel 5.10.235
    • Linux Kernel 5.15.179
    • Linux Kernel 6.1.130
    • Linux Kernel 6.6.80
    • Linux Kernel 6.12.17
    • Linux Kernel 6.13.5
    • Linux Kernel 6.14

    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: Siemens ProductCERT, BSI, SUSE, Debian LTS, Red Hat, Debian, CVE.org, Msrc Update Guide, EUVD

    0.3 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 16.7

    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
    37.88 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
    0.3 %
    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
    16.7
    Elevated — this CVE ranks above at least 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: partial
    Source: CISA Vulnrichment, as of 1 October 2025
    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-476

    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: acct: perform last write from workqueue In [1] it was reported that the acct(2) system call can be used to trigger NULL deref in cases where it is set to write to a file that triggers an internal lookup. This can e.g., happen when pointing acc(2) to /sys/power/resume. At the point the where the write to this file happens the calling task has already exited and called exit_fs(). A lookup will thus trigger a NULL-deref when accessing current->fs. Reorganize the code so that the the final write happens from the workqueue but with the caller's credentials. This preserves the (strange) permission model and has almost no regression risk. This api should stop to exist though.

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

    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 – < 6.12.17
    • 5.5 – < 5.10.235
    • 5.16 – < 6.1.130
    • 6.2 – < 6.6.80
    • 2.6.12 – < 5.4.291
    • —
    • 5.11 – < 5.15.179
    • 6.13 – < 6.13.5
    • 6.12.17
    • 5.10.235
    • 6.1.130
    • 6.6.80
    • 5.4.291
    • 6.14
    • 5.15.179
    • 6.13.5
    DellSecure Connect Gateway
    • < 5.30.0.14
    • 5.30.0.14
    IBMSecurity Verify Access
    • < 10.0.9.2
    • 10.0.9.2
    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_kernel6.14
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-476NULL Pointer Dereference

      Base

      The product dereferences a pointer that it expects to be valid but is NULL.

      Entry at MITRE CWE-476

    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
      —
      https://git.kernel.org/stable/c/56d5f3eba3f5de0efdd556de4ef381e109b973a9
      Referenceadded
      —
      https://git.kernel.org/stable/c/5a59ced8ffc71973d42c82484a719c8f6ac8f7f7
      Referenceadded
      —
      https://git.kernel.org/stable/c/5c928e14a2ccd99462f2351ead627b58075bb736
      Referenceadded
      —
      https://git.kernel.org/stable/c/5d5b936cfa4b0d5670ca7420ef165a074bc008eb
      Referenceadded
      —
      https://git.kernel.org/stable/c/5ee8da9bea70dda492d61f075658939af33d8410
      Referenceadded
      —
      https://git.kernel.org/stable/c/8acbf4a88c6a98c8ed00afd1a7d1abcca9b4735e
      Referenceadded
      —
      https://git.kernel.org/stable/c/a8136afca090412a36429cb6c2543c714d9c0f84
      Referenceadded
      —
      https://git.kernel.org/stable/c/b03782ae707cc45e65242c7cddd8e28f1c22cde5
      Referenceremoved
      https://git.kernel.org/stable/c/56d5f3eba3f5de0efdd556de4ef381e109b973a9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5a59ced8ffc71973d42c82484a719c8f6ac8f7f7
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5c928e14a2ccd99462f2351ead627b58075bb736
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5d5b936cfa4b0d5670ca7420ef165a074bc008eb
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5ee8da9bea70dda492d61f075658939af33d8410
      —
      Referenceremoved
      https://git.kernel.org/stable/c/8acbf4a88c6a98c8ed00afd1a7d1abcca9b4735e
      —
      Referenceremoved
      https://git.kernel.org/stable/c/a8136afca090412a36429cb6c2543c714d9c0f84
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b03782ae707cc45e65242c7cddd8e28f1c22cde5
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/56d5f3eba3f5de0efdd556de4ef381e109b973a9 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/5a59ced8ffc71973d42c82484a719c8f6ac8f7f7 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/5c928e14a2ccd99462f2351ead627b58075bb736 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/5d5b936cfa4b0d5670ca7420ef165a074bc008eb Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/5ee8da9bea70dda492d61f075658939af33d8410 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8acbf4a88c6a98c8ed00afd1a7d1abcca9b4735e Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/a8136afca090412a36429cb6c2543c714d9c0f84 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b03782ae707cc45e65242c7cddd8e28f1c22cde5 Types: Patch
      —

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

    2. Record modifiedCVE Program

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
      Referenceadded
      —
      https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html
      Referenceremoved
      https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
      —
      Referenceremoved
      https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html
      —

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

    3. Record modifiedSiemens ADP

      Show 7 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/2025/21xxx/CVE-2025-21846.json">CVE-2025-21846</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-265688.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      —
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-265688.html
      —

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

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