HighCVE-2026-53397

    Linux Kernel: security vulnerability (CVE-2026-53397)

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

    What is affected, what to do

    A flaw was found in the Linux kernel's Network File System Daemon (nfsd). This vulnerability occurs during the processing of Access Control List (ACL) set operations.

    Update Linux Kernel to version 5.10.260, Linux Kernel to version 5.15.211, Linux Kernel to version 6.1.177.

    Affected
    • Linux Kernel lt 2.6.13..5.10.260
    • 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 5.15.211
    • 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

    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, Debian LTS, Red Hat, 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
    74.50 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-401

    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 Network File System Daemon (nfsd). This vulnerability occurs during the processing of Access Control List (ACL) set operations. If a specific decode step fails, a memory leak of a posix_acl object occurs. This can lead to resource exhaustion over time, potentially resulting in a Denial of Service (DoS) for the affected server.

    Source: suse_csaf, Ubuntu Security Notices, Debian LTS Advisories, redhat_csaf, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), Microsoft Security Update Guide, 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
    • 5.16 – < 6.1.177
    • 5.11 – < 5.15.211
    • 6.7 – < 6.12.95
    • 6.2 – < 6.6.144
    • 6.13 – < 6.18.38
    • —
    • 6.19 – < 7.1.3
    • 2.6.13 – < 5.10.260
    • 6.1.177
    • 5.15.211
    • 6.12.95
    • 6.6.144
    • 6.18.38
    • 7.2
    • 7.1.3
    • 5.10.260
    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
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-401Missing Release of Memory after Effective Lifetime

      Variant

      The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

      Entry at MITRE CWE-401

    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-401

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-401

      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/0853ac544c590880d797b04daa33fcb72b6be0e1
      Referenceadded
      —
      https://git.kernel.org/stable/c/136b416593f1349cf6f72c8e3d18f0f204ee8545
      Referenceadded
      —
      https://git.kernel.org/stable/c/1e96239fddcefacf6afe6c498357be68eacbcabc
      Referenceadded
      —
      https://git.kernel.org/stable/c/887f92ceccf3eacd5f2402db21254d66372fae00
      Referenceadded
      —
      https://git.kernel.org/stable/c/a5b42c1e4ff2befaa6b96f7cbf32174751eba083
      Referenceadded
      —
      https://git.kernel.org/stable/c/b2eb1ffd511d1b3c3e21122f97cbbccea411e277
      Referenceadded
      —
      https://git.kernel.org/stable/c/b94c4be77682aab06d65ca7296149e3bcfb37353
      Referenceadded
      —
      https://git.kernel.org/stable/c/bd69a825485168ef74e815ecb286754b570fdcc7
      Referenceremoved
      https://git.kernel.org/stable/c/0853ac544c590880d797b04daa33fcb72b6be0e1
      —
      Referenceremoved
      https://git.kernel.org/stable/c/136b416593f1349cf6f72c8e3d18f0f204ee8545
      —
      Referenceremoved
      https://git.kernel.org/stable/c/1e96239fddcefacf6afe6c498357be68eacbcabc
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      Referenceremoved
      https://git.kernel.org/stable/c/887f92ceccf3eacd5f2402db21254d66372fae00
      —
      Referenceremoved
      https://git.kernel.org/stable/c/a5b42c1e4ff2befaa6b96f7cbf32174751eba083
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b2eb1ffd511d1b3c3e21122f97cbbccea411e277
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b94c4be77682aab06d65ca7296149e3bcfb37353
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      Referenceremoved
      https://git.kernel.org/stable/c/bd69a825485168ef74e815ecb286754b570fdcc7
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/0853ac544c590880d797b04daa33fcb72b6be0e1 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/136b416593f1349cf6f72c8e3d18f0f204ee8545 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/1e96239fddcefacf6afe6c498357be68eacbcabc Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/887f92ceccf3eacd5f2402db21254d66372fae00 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/a5b42c1e4ff2befaa6b96f7cbf32174751eba083 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b2eb1ffd511d1b3c3e21122f97cbbccea411e277 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b94c4be77682aab06d65ca7296149e3bcfb37353 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/bd69a825485168ef74e815ecb286754b570fdcc7 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-2026-53397","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:30:22.806921Z"}

      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: nfsd: fix posix_acl leak on SETACL decode failure nfsaclsvc_decode_setaclargs() and nfs3svc_decode_setaclargs() each call nfs_stream_decode_acl() twice, first for NFS_ACL and then for NFS_DFACL. Each successful call transfers ownership of a freshly allocated posix_acl into argp->acl_access or argp->acl_default. If the first call succeeds but the second fails, the decoder returns false and argp->acl_access is left dangling. ACLPROC2_SETACL.pc_release was wired to nfssvc_release_attrstat and ACLPROC3_SETACL.pc_release was wired to nfs3svc_release_fhandle. Both only call fh_put() and have no knowledge of the ACL fields on argp. The posix_acl_release() pairs sat at the out: labels inside nfsacld_proc_setacl() and nfsd3_proc_setacl(), but svc_process() skips pc_func when pc_decode returns false, so that cleanup is unreachable on decode failure: svc_process_common() pc_decode() /* decode_setaclargs: false */ /* pc_func skipped */ pc_release() /* fh_put only -- ACLs leaked */ The orphaned posix_acl is leaked for the lifetime of the server. Fix by adding nfsaclsvc_release_setacl() and nfs3svc_release_setacl(), which release both argp->acl_access and argp->acl_default in addition to fh_put(), and wiring them as pc_release for their respective SETACL procedures. pc_release runs on every path svc_process() takes after decode, including decode failure, so the posix_acl_release() pairs are removed from the proc functions' out: labels to keep ownership in one place. This matches the existing release_getacl() pattern used by the sibling GETACL procedures.
      Referenceadded
      —
      https://git.kernel.org/stable/c/0853ac544c590880d797b04daa33fcb72b6be0e1
      Referenceadded
      —
      https://git.kernel.org/stable/c/136b416593f1349cf6f72c8e3d18f0f204ee8545
      Referenceadded
      —
      https://git.kernel.org/stable/c/1e96239fddcefacf6afe6c498357be68eacbcabc
      Referenceadded
      —
      https://git.kernel.org/stable/c/887f92ceccf3eacd5f2402db21254d66372fae00
      Referenceadded
      —
      https://git.kernel.org/stable/c/a5b42c1e4ff2befaa6b96f7cbf32174751eba083
      Referenceadded
      —
      https://git.kernel.org/stable/c/b2eb1ffd511d1b3c3e21122f97cbbccea411e277
      Referenceadded
      —
      https://git.kernel.org/stable/c/b94c4be77682aab06d65ca7296149e3bcfb37353
      Referenceadded
      —
      https://git.kernel.org/stable/c/bd69a825485168ef74e815ecb286754b570fdcc7

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

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