CriticalCVE-2026-63800

    Linux Kernel: Use After Free (CVE-2026-63800)

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

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    What is affected, what to do

    A flaw was found in the Linux kernel's parallel Network File System (pNFS) component. An issue in the `pnfs_update_layout()` function causes a use-after-free vulnerability due to incorrect ordering of memory management operations.

    Update Linux Kernel to version 5.10.260, Linux Kernel to version 5.5, Linux Kernel to version 5.15.211.

    Affected
    • Linux Kernel lt 5.10.9..5.10.260
    • Linux Kernel lt 5.4.91..5.5
    • Linux Kernel lt 5.11..5.15.211
    • Linux Kernel lt 5.16..6.1.177
    • Linux Kernel lt 6.2..6.6.144
    • Linux Kernel lt 6.7..6.12.95
    • Linux Kernel lt 6.13..6.18.38
    • Linux Kernel lt 6.19..7.1.3
    Fixed in
    • Linux Kernel 5.10.260
    • Linux Kernel 5.5
    • Linux Kernel 5.15.211
    • Linux Kernel 6.1.177
    • Linux Kernel 6.6.144
    • Linux Kernel 6.12.95
    • 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

    9.8

    Priority

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

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

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

    0.6 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 50.9

    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
    90.43 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
    0.6 %
    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
    50.9
    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 flaw was found in the Linux kernel's parallel Network File System (pNFS) component. An issue in the `pnfs_update_layout()` function causes a use-after-free vulnerability due to incorrect ordering of memory management operations. This flaw can be triggered when the system attempts to update a pNFS layout, potentially leading to system instability, crashes, or a denial of service. In some scenarios, this type of memory corruption could be exploited by a local attacker to achieve arbitrary code execution.

    Source: Ubuntu Security Notices, Debian LTS Advisories, redhat_csaf, Microsoft Security Update Guide, cvelistv5, NVD (NIST), 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
    • 5.4.91 – < 5.5
    • 5.16 – < 6.1.177
    • 5.11 – < 5.15.211
    • 5.10.9 – < 5.10.260
    • 6.7 – < 6.12.95
    • 6.2 – < 6.6.144
    • 6.13 – < 6.18.38
    • —
    • 6.19 – < 7.1.3
    • 5.5
    • 6.1.177
    • 5.15.211
    • 5.10.260
    • 6.12.95
    • 6.6.144
    • 6.18.38
    • 7.2
    • 7.1.3
    IBMQRadar SIEM
    • < 7.6.0.3
    • <7.5.0 UP16 IF01
    • 7.6.0.3
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbullseye
    Linuxubuntulinuxnoble
    Linuxdebianlinux-6.1bullseye
    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-oraclenoble
    Linuxubuntulinux-realtimenoble
    Linuxlinuxlinux_kernel5.11
    Linuxlinuxlinux_kernel—

    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/13e198a90ca4050f4bee8a3f23680389a6563ccc
      Referenceadded
      —
      https://git.kernel.org/stable/c/1f24b8302c77dcaf79c64c073877a3b9f4dd25d2
      Referenceadded
      —
      https://git.kernel.org/stable/c/200e7637f4d6a1342987045eea72641524f909dc
      Referenceadded
      —
      https://git.kernel.org/stable/c/2883ddd7542b4437a2ab4908fe2773f690e20889
      Referenceadded
      —
      https://git.kernel.org/stable/c/4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98
      Referenceadded
      —
      https://git.kernel.org/stable/c/7e37e9b3e82ade881e1798e2f4fcc54aff7793c1
      Referenceadded
      —
      https://git.kernel.org/stable/c/9645aaf689aff57427ece3b9fa47d5b5399417f4
      Referenceadded
      —
      https://git.kernel.org/stable/c/9c0fb5c09ae5bd68dc0038692af8127029cb0385
      Referenceremoved
      https://git.kernel.org/stable/c/13e198a90ca4050f4bee8a3f23680389a6563ccc
      —
      Referenceremoved
      https://git.kernel.org/stable/c/1f24b8302c77dcaf79c64c073877a3b9f4dd25d2
      —
      Referenceremoved
      https://git.kernel.org/stable/c/200e7637f4d6a1342987045eea72641524f909dc
      —
      Referenceremoved
      https://git.kernel.org/stable/c/2883ddd7542b4437a2ab4908fe2773f690e20889
      —
      Referenceremoved
      https://git.kernel.org/stable/c/4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98
      —
      Referenceremoved
      https://git.kernel.org/stable/c/7e37e9b3e82ade881e1798e2f4fcc54aff7793c1
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9645aaf689aff57427ece3b9fa47d5b5399417f4
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9c0fb5c09ae5bd68dc0038692af8127029cb0385
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/13e198a90ca4050f4bee8a3f23680389a6563ccc Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/1f24b8302c77dcaf79c64c073877a3b9f4dd25d2 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/200e7637f4d6a1342987045eea72641524f909dc Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/2883ddd7542b4437a2ab4908fe2773f690e20889 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/7e37e9b3e82ade881e1798e2f4fcc54aff7793c1 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/9645aaf689aff57427ece3b9fa47d5b5399417f4 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/9c0fb5c09ae5bd68dc0038692af8127029cb0385 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-2026-63800","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:30:40.400910Z"}

      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. ReceivedLinux

      Description added or changed

      Show 10 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: pNFS: Fix use-after-free in pnfs_update_layout() When hitting the NFS_LAYOUT_RETURN branch in pnfs_update_layout(), the code calls pnfs_prepare_to_retry_layoutget(lo). If it succeeds, pnfs_put_layout_hdr(lo) is called before trace_pnfs_update_layout(), which still references 'lo'. This results in a use-after-free when the tracepoint accesses lo's fields. Fix this by moving the tracepoint call before pnfs_put_layout_hdr(lo).
      Referenceadded
      —
      https://git.kernel.org/stable/c/13e198a90ca4050f4bee8a3f23680389a6563ccc
      Referenceadded
      —
      https://git.kernel.org/stable/c/1f24b8302c77dcaf79c64c073877a3b9f4dd25d2
      Referenceadded
      —
      https://git.kernel.org/stable/c/200e7637f4d6a1342987045eea72641524f909dc
      Referenceadded
      —
      https://git.kernel.org/stable/c/2883ddd7542b4437a2ab4908fe2773f690e20889
      Referenceadded
      —
      https://git.kernel.org/stable/c/4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98
      Referenceadded
      —
      https://git.kernel.org/stable/c/7e37e9b3e82ade881e1798e2f4fcc54aff7793c1
      Referenceadded
      —
      https://git.kernel.org/stable/c/9645aaf689aff57427ece3b9fa47d5b5399417f4
      Referenceadded
      —
      https://git.kernel.org/stable/c/9c0fb5c09ae5bd68dc0038692af8127029cb0385

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

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