CriticalCVE-2026-53399

    Linux Kernel: Use After Free (CVE-2026-53399)

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

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    What is affected, what to do

    A use-after-free flaw was found in the Linux kernel's NFS daemon (nfsd) pNFS layout handling. When nfsd4_layout_setlease fails, the layout stateid that was already published in the client IDR is freed directly, leaving a stale pointer in the IDR.

    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..6.18.39
    • 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 6.18.39
    • Linux Kernel 7.1.3
    • Linux Kernel 7.2

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

    Metrics

    9.8

    Priority

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

    Source: Vendor (CNA), CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

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

    0.7 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 51.7

    Show all metrics
    Severity
    Critical
    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
    91.11 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
    9.8 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
    9.8
    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
    0.7 %
    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
    51.7
    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: 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-416

    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 use-after-free flaw was found in the Linux kernel's NFS daemon (nfsd) pNFS layout handling. When nfsd4_layout_setlease fails, the layout stateid that was already published in the client IDR is freed directly, leaving a stale pointer in the IDR. A subsequent IDR traversal, such as states_show or client teardown, can dereference this freed memory. An attacker with NFS client access to an exported filesystem with pNFS enabled could exploit this flaw to crash the kernel (Denial of Service) or potentially achieve privilege escalation or arbitrary code execution through kernel memory corruption by reclaiming the freed slab object with attacker-controlled data.

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

    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 – < 6.18.39
    • 6.19 – < 7.1.3
    • 5.16 – < 6.1.178
    • 5.15.212
    • 6.6.145
    • 5.10.261
    • 6.12.96
    • 7.2
    • 6.18.39
    • 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-416Use After Free

      Variant

      The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

      Entry at MITRE CWE-416

    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-416

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-416

      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/2e0a5d6d62600b8c614d1b55e50ef94035d6adf9
      Referenceadded
      —
      https://git.kernel.org/stable/c/30d55c8aabb261bc3f427d6b9aae7ef6206063f9
      Referenceadded
      —
      https://git.kernel.org/stable/c/48a586e382e4db1dbf958d44b63e081df5f8ed04
      Referenceadded
      —
      https://git.kernel.org/stable/c/7bbb7ce74051c8be4b69ff44ce3db370600dae61
      Referenceadded
      —
      https://git.kernel.org/stable/c/83c2b7797742339bb768f83935f7ca33950db138
      Referenceadded
      —
      https://git.kernel.org/stable/c/8dee7c278f1c2b5bb80e17a6281c3812fc8b0cdd
      Referenceadded
      —
      https://git.kernel.org/stable/c/d369e5edfaaf83a448016e2f1da392b2174be801
      Referenceadded
      —
      https://git.kernel.org/stable/c/d788ef40a7517d22c97ab01700e4ae4c611b6f2f
      Referenceremoved
      https://git.kernel.org/stable/c/2e0a5d6d62600b8c614d1b55e50ef94035d6adf9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/30d55c8aabb261bc3f427d6b9aae7ef6206063f9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/48a586e382e4db1dbf958d44b63e081df5f8ed04
      —
      Referenceremoved
      https://git.kernel.org/stable/c/7bbb7ce74051c8be4b69ff44ce3db370600dae61
      —
      Referenceremoved
      https://git.kernel.org/stable/c/83c2b7797742339bb768f83935f7ca33950db138
      —
      Referenceremoved
      https://git.kernel.org/stable/c/8dee7c278f1c2b5bb80e17a6281c3812fc8b0cdd
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d369e5edfaaf83a448016e2f1da392b2174be801
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d788ef40a7517d22c97ab01700e4ae4c611b6f2f
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/2e0a5d6d62600b8c614d1b55e50ef94035d6adf9 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/30d55c8aabb261bc3f427d6b9aae7ef6206063f9 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/48a586e382e4db1dbf958d44b63e081df5f8ed04 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/7bbb7ce74051c8be4b69ff44ce3db370600dae61 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/83c2b7797742339bb768f83935f7ca33950db138 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8dee7c278f1c2b5bb80e17a6281c3812fc8b0cdd Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d369e5edfaaf83a448016e2f1da392b2174be801 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d788ef40a7517d22c97ab01700e4ae4c611b6f2f 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-2026-53399","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:30:28.051870Z"}

      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/2e0a5d6d62600b8c614d1b55e50ef94035d6adf9
      Referenceadded
      —
      https://git.kernel.org/stable/c/48a586e382e4db1dbf958d44b63e081df5f8ed04
      Referenceadded
      —
      https://git.kernel.org/stable/c/7bbb7ce74051c8be4b69ff44ce3db370600dae61
      Referenceadded
      —
      https://git.kernel.org/stable/c/d788ef40a7517d22c97ab01700e4ae4c611b6f2f
      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: nfsd: release layout stid on setlease failure nfs4_alloc_stid() publishes the new stid into cl->cl_stateids via idr_alloc_cyclic() under cl_lock before returning to nfsd4_alloc_layout_stateid(). When nfsd4_layout_setlease() then fails, the error path frees the layout stateid directly with kmem_cache_free() without ever calling idr_remove(), leaving the IDR slot pointing at freed slab memory. Any subsequent IDR walker (states_show, client teardown) dereferences the dangling pointer. The correct teardown for an IDR-published stid is nfs4_put_stid(), which removes the IDR slot under cl_lock, dispatches sc_free (nfsd4_free_layout_stateid) to release ls->ls_file via nfsd4_close_layout(), and drops the nfs4_file reference in its tail. A second issue blocks that switch: nfsd4_free_layout_stateid() unconditionally inspects ls->ls_fence_work via delayed_work_pending() under ls_lock, but INIT_DELAYED_WORK(&ls->ls_fence_work, ...) currently runs only after the setlease call. On the setlease-failure path the destructor would touch an uninitialized delayed_work. nfsd4_alloc_layout_stateid() nfs4_alloc_stid() /* idr_alloc_cyclic under cl_lock */ nfsd4_layout_setlease() /* fails */ nfs4_put_stid() nfsd4_free_layout_stateid() delayed_work_pending(&ls->ls_fence_work) /* needs INIT */ nfsd4_close_layout() /* nfsd_file_put(ls->ls_file) */ put_nfs4_file() Fix by hoisting the ls_fenced / ls_fence_delay / INIT_DELAYED_WORK initialization above the nfsd4_layout_setlease() call, and replace the manual nfsd_file_put + put_nfs4_file + kmem_cache_free cleanup with a single nfs4_put_stid(stp).
      Referenceadded
      —
      https://git.kernel.org/stable/c/30d55c8aabb261bc3f427d6b9aae7ef6206063f9
      Referenceadded
      —
      https://git.kernel.org/stable/c/83c2b7797742339bb768f83935f7ca33950db138
      Referenceadded
      —
      https://git.kernel.org/stable/c/8dee7c278f1c2b5bb80e17a6281c3812fc8b0cdd
      Referenceadded
      —
      https://git.kernel.org/stable/c/d369e5edfaaf83a448016e2f1da392b2174be801

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

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