CriticalCVE-2026-31402

    Linux Kernel: Out-of-Bounds Write (CVE-2026-31402)

    Published Last modified Sources: Siemens ProductCERT, Ubuntu, Debian LTS, Debian, BSI, SUSE, CVE.org, EUVD

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses. This size was calculated based on OPEN responses and does not account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT).

    Update Linux Kernel to version 5.10.253, Linux Kernel to version 5.15.210, Linux Kernel to version 6.1.167.

    Affected
    • Linux Kernel lt 2.6.12..5.10.253
    • Linux Kernel lt 5.11..5.15.210
    • Linux Kernel lt 5.16..6.1.167
    • Linux Kernel lt 6.2..6.6.130
    • Linux Kernel lt 6.7..6.12.78
    • Linux Kernel lt 6.13..6.18.20
    • Linux Kernel lt 6.19..6.19.10
    • Linux Kernel lt 6.20..7.0
    Fixed in
    • Linux Kernel 5.10.253
    • Linux Kernel 5.15.210
    • Linux Kernel 6.1.167
    • Linux Kernel 6.6.130
    • Linux Kernel 6.12.78
    • Linux Kernel 6.18.20
    • Linux Kernel 6.19.10
    • Linux Kernel 7.0

    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: Siemens ProductCERT, Ubuntu, Debian LTS, Debian, BSI, SUSE, CVE.org, EUVD

    1.2 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 68.1

    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
    101.85 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
    1.2 %
    Moderate — model estimates 1-10% 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
    68.1
    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-122

    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: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses. This size was calculated based on OPEN responses and does not account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a LOCK operation is denied due to a conflict with an existing lock that has a large owner, nfsd4_encode_operation() copies the full encoded response into the undersized replay buffer via read_bytes_from_xdr_buf() with no bounds check. This results in a slab-out-of-bounds write of up to 944 bytes past the end of the buffer, corrupting adjacent heap memory. This can be triggered remotely by an unauthenticated attacker with two cooperating NFSv4.0 clients: one sets a lock with a large owner string, then the other requests a conflicting lock to provoke the denial. We could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a full opaque, but that would increase the size of every stateowner, when most lockowners are not that large. Instead, fix this by checking the encoded response length against NFSD4_REPLAY_ISIZE before copying into the replay buffer. If the response is too large, set rp_buflen to 0 to skip caching the replay payload. The status is still cached, and the client already received the correct response on the original request.

    Source: siemens_advisory, Ubuntu Security Notices, Debian LTS Advisories, Debian Security Advisories, BSI WID Portal, BSI CSAF, suse_csaf, cvelistv5, ENISA EUVD, NVD (NIST), 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
    • 6.2 – < 6.6.130
    • 6.7 – < 6.12.78
    • 5.11 – < 5.15.210
    • 2.6.12 – < 5.10.253
    • 6.19 – < 6.19.10
    • 6.13 – < 6.18.20
    • 6.20 – < 7.0
    • 5.16 – < 6.1.167
    • 6.6.130
    • 6.12.78
    • 5.15.210
    • 5.10.253
    • 6.19.10
    • 6.18.20
    • 7.0
    • 6.1.167
    IBMQRadar SIEM
    • <7.5.0 UP15 IF03
    • —
    IBMSecurity Verify Access
    • < 10.0.9.2
    • 10.0.9.2
    MicrosoftAzure Linux
    • azl3
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinuxtrixie
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel2.6.12
    Linuxlinuxlinux_kernel7.0
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-122Heap-based Buffer Overflow

      Variant

      A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

      Entry at MITRE CWE-122

    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-122

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      CWE-122

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

    2. Record modifiedCISA ADP

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

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      TypeActionBeforeAfter
      SSVC assessmentadded
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      {"id":"CVE-2026-31402","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:08:51.430825Z"}

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

    3. Record modifiedLinux

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      https://git.kernel.org/stable/c/0f0e2a54a31a7f9ad2915db99156114872317388
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      https://git.kernel.org/stable/c/2665887a69437a8a4f552f69509eecfb73d4aa19
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      https://git.kernel.org/stable/c/5133b61aaf437e5f25b1b396b14242a6bb0508e2
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      https://git.kernel.org/stable/c/8afb437ea1f70cacb4bbdf11771fb5c4d720b965
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      https://git.kernel.org/stable/c/ae8498337dfdfda71bdd0b807c9a23a126011d76
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      https://git.kernel.org/stable/c/c9452c0797c95cf2378170df96cf4f4b3bca7eff
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      https://git.kernel.org/stable/c/dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0
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      https://git.kernel.org/stable/c/f9fcb4441f6c02bb20c2eb340101e27dfe23607c
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      https://git.kernel.org/stable/c/0f0e2a54a31a7f9ad2915db99156114872317388
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      https://git.kernel.org/stable/c/2665887a69437a8a4f552f69509eecfb73d4aa19
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      https://git.kernel.org/stable/c/5133b61aaf437e5f25b1b396b14242a6bb0508e2
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      https://git.kernel.org/stable/c/ae8498337dfdfda71bdd0b807c9a23a126011d76
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      https://git.kernel.org/stable/c/c9452c0797c95cf2378170df96cf4f4b3bca7eff
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      https://git.kernel.org/stable/c/dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0
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      https://git.kernel.org/stable/c/f9fcb4441f6c02bb20c2eb340101e27dfe23607c
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      https://git.kernel.org/stable/c/0f0e2a54a31a7f9ad2915db99156114872317388 Types: Patch
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      https://git.kernel.org/stable/c/5133b61aaf437e5f25b1b396b14242a6bb0508e2 Types: Patch
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      https://git.kernel.org/stable/c/8afb437ea1f70cacb4bbdf11771fb5c4d720b965 Types: Patch
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      Reference typeremoved
      https://git.kernel.org/stable/c/ae8498337dfdfda71bdd0b807c9a23a126011d76 Types: Patch
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      https://git.kernel.org/stable/c/c9452c0797c95cf2378170df96cf4f4b3bca7eff Types: Patch
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      https://git.kernel.org/stable/c/dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0 Types: Patch
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      Reference typeremoved
      https://git.kernel.org/stable/c/f9fcb4441f6c02bb20c2eb340101e27dfe23607c Types: Patch
      —

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

    4. Record modifiedRed Hat ADP

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      https://access.redhat.com/errata/RHSA-2026:10108
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      https://access.redhat.com/errata/RHSA-2026:11313
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      https://access.redhat.com/errata/RHSA-2026:13565
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      https://access.redhat.com/errata/RHSA-2026:13566
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      https://access.redhat.com/errata/RHSA-2026:13577
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      https://access.redhat.com/errata/RHSA-2026:13578
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      https://access.redhat.com/errata/RHSA-2026:13664
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      https://access.redhat.com/errata/RHSA-2026:13681
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      https://access.redhat.com/errata/RHSA-2026:13734
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      https://access.redhat.com/errata/RHSA-2026:13936
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      https://access.redhat.com/errata/RHSA-2026:14137
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      https://access.redhat.com/errata/RHSA-2026:14165
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      https://access.redhat.com/errata/RHSA-2026:14301
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      https://access.redhat.com/errata/RHSA-2026:14823
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      https://access.redhat.com/errata/RHSA-2026:14869
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      https://access.redhat.com/errata/RHSA-2026:14925
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      https://access.redhat.com/errata/RHSA-2026:15883
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      https://access.redhat.com/errata/RHSA-2026:19568
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      https://access.redhat.com/errata/RHSA-2026:19569
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      https://access.redhat.com/errata/RHSA-2026:36530
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      https://access.redhat.com/errata/RHSA-2026:36534
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      https://access.redhat.com/security/cve/CVE-2026-31402
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      https://bugzilla.redhat.com/show_bug.cgi?id=2454844
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      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31402.json
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      https://access.redhat.com/errata/RHSA-2026:10108
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      https://access.redhat.com/errata/RHSA-2026:11313
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      https://access.redhat.com/errata/RHSA-2026:13566
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      https://access.redhat.com/errata/RHSA-2026:13577
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      https://access.redhat.com/errata/RHSA-2026:13664
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      https://access.redhat.com/errata/RHSA-2026:13681
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      https://access.redhat.com/errata/RHSA-2026:19568
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      https://access.redhat.com/errata/RHSA-2026:19569
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      https://access.redhat.com/errata/RHSA-2026:36530
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      https://access.redhat.com/errata/RHSA-2026:36531
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      https://access.redhat.com/errata/RHSA-2026:36533
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      https://access.redhat.com/errata/RHSA-2026:36534
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      https://access.redhat.com/security/cve/CVE-2026-31402
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      https://bugzilla.redhat.com/show_bug.cgi?id=2454844
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      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31402.json
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      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    5. Record modifiedSiemens ADP

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      TypeActionBeforeAfter
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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/31xxx/CVE-2026-31402.json">CVE-2026-31402</a>
      Referenceadded
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      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      Referenceadded
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      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
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      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
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      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      —
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
      —

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

    Show one older change

    1. Record modifiedLinux

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
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      https://git.kernel.org/stable/c/2665887a69437a8a4f552f69509eecfb73d4aa19
      Affected versions (publisher)changed
      Linux, Linux
      Linux, Linux

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

    One NVD translation into another language is hidden.

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    Badge preview for CVE-2026-31402
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-31402"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-31402.svg?lang=en" alt="CVE-2026-31402 – NEOSEC Intel" height="20"></a>