HighCVE-2026-53392

    Linux Kernel: Improper Input Validation (CVE-2026-53392)

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

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    What is affected, what to do

    A flaw was found in the Linux kernel's NFSv4 (Network File System version 4) flexfiles component. This vulnerability occurs when the ff_layout_alloc_lseg() function processes a malformed flexfiles layout that specifies a zero filehandle version count.

    Update Linux Kernel to version 5.10.261, Linux Kernel to version 5.15.212, Linux Kernel to version 6.1.178.

    Affected
    • Linux Kernel lt 4.0..5.10.261
    • Linux Kernel lt 5.11..5.15.212
    • Linux Kernel lt 5.16..6.1.178
    • Linux Kernel lt 6.2..6.6.145
    • Linux Kernel lt 6.7..6.12.96
    • Linux Kernel lt 6.13..6.18.38
    • Linux Kernel lt 6.19..7.1.3
    Fixed in
    • Linux Kernel 5.10.261
    • Linux Kernel 5.15.212
    • Linux Kernel 6.1.178
    • Linux Kernel 6.6.145
    • Linux Kernel 6.12.96
    • Linux Kernel 6.18.38
    • Linux Kernel 7.1.3
    • Linux Kernel 7.2

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

    Metrics

    7.5

    Priority

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

    Source: Vendor (CNA), CVSS v3

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: SUSE, Ubuntu, Red Hat, Debian LTS, Debian, BSI, CVE.org, Msrc Update Guide

    0.5 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 44.8

    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
    74.26 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
    7.5 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
    7.5
    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
    0.5 %
    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
    44.8
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    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 · automatable · Technical impact: partial
    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-20

    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

    A flaw was found in the Linux kernel's NFSv4 (Network File System version 4) flexfiles component. This vulnerability occurs when the ff_layout_alloc_lseg() function processes a malformed flexfiles layout that specifies a zero filehandle version count. An attacker could exploit this by providing a specially crafted flexfiles layout, leading to a null-pointer dereference and ultimately causing a kernel panic, resulting in a Denial of Service (DoS) for the system.

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

    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
    • 5.11 – < 5.15.212
    • 6.2 – < 6.6.145
    • 4.0 – < 5.10.261
    • 6.7 – < 6.12.96
    • 6.13 – < 6.18.38
    • —
    • 6.19 – < 7.1.3
    • 5.16 – < 6.1.178
    • 5.15.212
    • 6.6.145
    • 5.10.261
    • 6.12.96
    • 6.18.38
    • 7.2
    • 7.1.3
    • 6.1.178
    IBMQRadar SIEM
    • < 7.6.0.3
    • <7.5.0 UP16 IF01
    • 7.6.0.3
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinuxtrixie
    Linuxubuntulinuxnoble
    Linuxdebianlinux-6.1bullseye
    Linuxdebianlinux-6.12bookworm
    Linuxubuntulinux-awsnoble
    Linuxubuntulinux-aws-fipsnoble
    Linuxubuntulinux-azurenoble
    Linuxubuntulinux-azure-fdenoble
    Linuxubuntulinux-azure-fipsnoble
    Linuxubuntulinux-fipsnoble
    Linuxubuntulinux-gcpnoble
    Linuxubuntulinux-gcp-fipsnoble
    Linuxubuntulinux-gkenoble
    Linuxubuntulinux-gkeopnoble
    Linuxubuntulinux-ibmnoble
    Linuxubuntulinux-lowlatencynoble
    Linuxubuntulinux-nvidiajammy
    Linuxubuntulinux-nvidia-tegrajammy
    Linuxubuntulinux-nvidia-tegra-5.15focal
    Linuxubuntulinux-nvidia-tegra-igxjammy
    Linuxubuntulinux-oraclenoble
    Linuxubuntulinux-realtimenoble

    Weakness classes (CWE)

    • CWE-20Improper Input Validation

      Class

      The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

      Entry at MITRE CWE-20

    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-20

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-20

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

    2. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/18cc6d57a14fa65ab2a2b52279f549041c4bc9cf
      Referenceadded
      —
      https://git.kernel.org/stable/c/2131ed64b767ffa8bcdb3677d90f3964e39aabc8
      Referenceadded
      —
      https://git.kernel.org/stable/c/2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2
      Referenceadded
      —
      https://git.kernel.org/stable/c/7779c85028a0676fb190cde4f0c540f4f8e97761
      Referenceadded
      —
      https://git.kernel.org/stable/c/9033591535c066726f5b505126ccb4068b98fa4f
      Referenceadded
      —
      https://git.kernel.org/stable/c/be7829715e341b42846437dd9e721005db59f0cc
      Referenceadded
      —
      https://git.kernel.org/stable/c/d8c90c7cc061265d5f2813a1f5c82ef2f4707e67
      Referenceadded
      —
      https://git.kernel.org/stable/c/eeabb9020721db6bc132e68eeae380b8d4fb4b04
      Referenceremoved
      https://git.kernel.org/stable/c/18cc6d57a14fa65ab2a2b52279f549041c4bc9cf
      —
      Referenceremoved
      https://git.kernel.org/stable/c/2131ed64b767ffa8bcdb3677d90f3964e39aabc8
      —
      Referenceremoved
      https://git.kernel.org/stable/c/2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2
      —
      Referenceremoved
      https://git.kernel.org/stable/c/7779c85028a0676fb190cde4f0c540f4f8e97761
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9033591535c066726f5b505126ccb4068b98fa4f
      —
      Referenceremoved
      https://git.kernel.org/stable/c/be7829715e341b42846437dd9e721005db59f0cc
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d8c90c7cc061265d5f2813a1f5c82ef2f4707e67
      —
      Referenceremoved
      https://git.kernel.org/stable/c/eeabb9020721db6bc132e68eeae380b8d4fb4b04
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/18cc6d57a14fa65ab2a2b52279f549041c4bc9cf Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/2131ed64b767ffa8bcdb3677d90f3964e39aabc8 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/7779c85028a0676fb190cde4f0c540f4f8e97761 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/9033591535c066726f5b505126ccb4068b98fa4f Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/be7829715e341b42846437dd9e721005db59f0cc Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d8c90c7cc061265d5f2813a1f5c82ef2f4707e67 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/eeabb9020721db6bc132e68eeae380b8d4fb4b04 Types: Patch
      —

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

    3. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: yes

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-53392","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:30:14.556570Z"}

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

    4. Record modifiedLinux

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      Linux, Linux
      Linux, Linux

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

    5. Record modifiedLinux

      Show 5 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/18cc6d57a14fa65ab2a2b52279f549041c4bc9cf
      Referenceadded
      —
      https://git.kernel.org/stable/c/9033591535c066726f5b505126ccb4068b98fa4f
      Referenceadded
      —
      https://git.kernel.org/stable/c/be7829715e341b42846437dd9e721005db59f0cc
      Referenceadded
      —
      https://git.kernel.org/stable/c/eeabb9020721db6bc132e68eeae380b8d4fb4b04
      Affected versions (publisher)changed
      Linux, Linux
      Linux, Linux

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

    Show one older change

    1. ReceivedLinux

      Description added or changed

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Linux, Linux
      Descriptionadded
      —
      In the Linux kernel, the following vulnerability has been resolved: NFSv4/flexfiles: reject zero filehandle version count ff_layout_alloc_lseg() decodes the filehandle-version array count from the flexfiles layout body. The value is used as the count for kzalloc_objs(), and the current code only rejects NULL. A zero count yields ZERO_SIZE_PTR, which can be stored in dss_info->fh_versions even though later flexfiles paths assume that at least one filehandle version exists. Reject fh_count == 0 before the allocation, matching the existing zero version_count validation in the flexfiles GETDEVICEINFO parser. A QEMU/KASAN run with a malformed flexfiles layout hit: KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:ff_layout_encode_ff_layoutupdate.isra.0+0x15f/0x750 ff_layout_encode_layoutreturn+0x683/0x970 nfs4_xdr_enc_layoutreturn+0x278/0x3a0 Kernel panic - not syncing: Fatal exception The patched kernel rejects the malformed layout without KASAN/oops/panic, and a valid fh_count=1 regression still opens, reads, and unmounts cleanly.
      Referenceadded
      —
      https://git.kernel.org/stable/c/2131ed64b767ffa8bcdb3677d90f3964e39aabc8
      Referenceadded
      —
      https://git.kernel.org/stable/c/2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2
      Referenceadded
      —
      https://git.kernel.org/stable/c/7779c85028a0676fb190cde4f0c540f4f8e97761
      Referenceadded
      —
      https://git.kernel.org/stable/c/d8c90c7cc061265d5f2813a1f5c82ef2f4707e67

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

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