HighCVE-2026-31694

    Linux Kernel: security vulnerability (CVE-2026-31694)

    Published Last modified Sources: Ubuntu, SUSE, 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: fuse: reject oversized dirents in page cache fuse_add_dirent_to_cache() computes a serialized dirent size from the server-controlled namelen field and copies the dirent into a single page-cache page. The existing logic only checks whether the dirent fits in the remaining space of the current page and advances to a fresh page if not.

    An exploit is publicly available. Update Linux Kernel to version 6.18.25, Linux Kernel to version 7.0.2, Linux Kernel to version 7.1.

    Affected
    • Linux Kernel lt 6.15..6.18.25
    • Linux Kernel lt 6.19..7.0.2
    Fixed in
    • Linux Kernel 6.18.25
    • Linux Kernel 7.0.2
    • 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: NVD, CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

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

    0.3 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 21.0

    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
    59.34 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
    PoC (publicly reported)
    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
    0.3 %
    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
    21.0
    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

    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: fuse: reject oversized dirents in page cache fuse_add_dirent_to_cache() computes a serialized dirent size from the server-controlled namelen field and copies the dirent into a single page-cache page. The existing logic only checks whether the dirent fits in the remaining space of the current page and advances to a fresh page if not. It never checks whether the dirent itself exceeds PAGE_SIZE. As a result, a malicious FUSE server can return a dirent with namelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB page systems this causes memcpy() to overflow the cache page by 24 bytes into the following kernel page. Reject dirents that cannot fit in a single page before copying them into the readdir cache.

    Source: Ubuntu Security Notices, suse_csaf, siemens_advisory, BSI WID Portal, BSI CSAF, NVD (NIST), cvelistv5, 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
    • 6.15 – < 6.18.25
    • —
    • 6.19 – < 7.0.2
    • 6.18.25
    • 7.1
    • 7.0.2
    MicrosoftAzure Linux
    • azl3
    • —
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxubuntuawsbionic
    Linuxubuntuawsjammy
    Linuxubuntuawsnoble
    Linuxubuntuawsresolute
    Linuxubuntuawsxenial
    Linuxubuntuaws-6.8jammy
    Linuxubuntuaws-hwexenial
    Linuxubuntuazurejammy
    Linuxubuntuazurenoble
    Linuxubuntuazureresolute
    Linuxubuntuazurexenial
    Linuxubuntuazure-4.15bionic
    Linuxubuntugcpjammy
    Linuxubuntugcpnoble
    Linuxubuntugcpresolute
    Linuxubuntugcpxenial
    Linuxubuntugcp-4.15bionic
    Linuxubuntugcp-6.8jammy
    Linuxubuntugeneric-4.15bionic
    Linuxubuntugeneric-4.15xenial
    Linuxubuntugeneric-4.4xenial
    Linuxubuntugeneric-5.4bionic
    Linuxubuntugeneric-5.4focal
    Linuxubuntugkejammy

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    PoC-in-GitHub (nomi-sec)CVE-2026-31694-POC (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    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. NVD analysis modifiedNVD

      Product mapping changed:
      • Linux Kernel (6.19 – before 7.0.2; 6.15 – before 6.18.25; 2 individual versions)
      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      AND OR *cpe:2.3:o:siemens:simatic_s7-1500_tm_mfp_firmware:-:*:*:*:*:*:*:* OR cpe:2.3:h:siemens:simatic_s7-1500_tm_mfp:-:*:*:*:*:*:*:*
      Product configurationchanged
      OR *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.12.84 *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:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.18.25 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.2 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 4.20 up to (excluding) 6.6.136
      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:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.2 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.15 up to (excluding) 6.18.25
      Reference typeadded
      —
      siemens-SADP: https://cert-portal.siemens.com/productcert/html/ssa-784472.html Types: Third Party Advisory

      Source identifier: nvd@nist.gov

    2. Record modifiedLinux

      Show 9 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/474ce83c96a55f2eeb14dee2be375eeadfdacdf5
      Referenceadded
      —
      https://git.kernel.org/stable/c/51a8de6c50bf947c8f534cd73da4c8f0a13e7bed
      Referenceadded
      —
      https://git.kernel.org/stable/c/7de93abfaae1b2dc94da8a07a36421bd073f1d8f
      Referenceremoved
      https://git.kernel.org/stable/c/474ce83c96a55f2eeb14dee2be375eeadfdacdf5
      —
      Referenceremoved
      https://git.kernel.org/stable/c/51a8de6c50bf947c8f534cd73da4c8f0a13e7bed
      —
      Referenceremoved
      https://git.kernel.org/stable/c/7de93abfaae1b2dc94da8a07a36421bd073f1d8f
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/474ce83c96a55f2eeb14dee2be375eeadfdacdf5 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/51a8de6c50bf947c8f534cd73da4c8f0a13e7bed Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/7de93abfaae1b2dc94da8a07a36421bd073f1d8f 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/2026/31xxx/CVE-2026-31694.json">CVE-2026-31694</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

    4. Record modifiedLinux

      8 individual changes: Affected versions (publisher), Reference, Reference type

      Show 8 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      Linux, Linux
      Linux, Linux
      Referenceremoved
      https://git.kernel.org/stable/c/038e61812fa52ef62bad2cfc96bf37dc0db47c1e
      —
      Referenceremoved
      https://git.kernel.org/stable/c/1d4a517fa90480c52fd452fea2686cd80f773ce2
      —
      Referenceremoved
      https://git.kernel.org/stable/c/3059f9abe7f1ba8fddf3c86c5faa1eeacf07e7d4
      —
      Referenceremoved
      https://git.kernel.org/stable/c/45c05af36311624c1148123caeb011312495d86b
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d23ad78bfd205eac26766e38ba7d79f279131098
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/45c05af36311624c1148123caeb011312495d86b Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d23ad78bfd205eac26766e38ba7d79f279131098 Types: Patch
      —

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

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