HighCVE-2026-53391

    Linux Kernel: NULL Pointer Dereference (CVE-2026-53391)

    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 NFSv4/pNFS implementation. The `nfs4_decode_mp_ds_addr` function, responsible for decoding network address information, does not properly handle zero-length `r_addr` opaque data.

    Update Linux Kernel to version 5.15.211, Linux Kernel to version 6.1.177, Linux Kernel to version 6.6.144.

    Affected
    • Linux Kernel lt 4.0..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 5.15.211
    • 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 44.0

    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
    73.85 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
    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
    44.0
    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-476

    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/pNFS implementation. The `nfs4_decode_mp_ds_addr` function, responsible for decoding network address information, does not properly handle zero-length `r_addr` opaque data. A malicious or compromised metadata server can exploit this by providing a zero-length `r_addr`, leading to a NULL pointer dereference and causing the client system to panic, resulting in a Denial of Service (DoS).

    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
    • 4.0 – < 5.15.211
    • 6.7 – < 6.12.95
    • 6.2 – < 6.6.144
    • 6.13 – < 6.18.38
    • —
    • 6.19 – < 7.1.3
    • 6.1.177
    • 5.15.211
    • 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
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-476NULL Pointer Dereference

      Base

      The product dereferences a pointer that it expects to be valid but is NULL.

      Entry at MITRE CWE-476

    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-476

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-476

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

    2. Record modifiedLinux

      Show 21 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/012d37a568bfbb2c9686f03ade75560bc7139956
      Referenceadded
      —
      https://git.kernel.org/stable/c/30aae62e50b4e074a90a9a5e15246548fbdc1182
      Referenceadded
      —
      https://git.kernel.org/stable/c/41fe0f7b84f0cb822ae10ab08592996a592b2a25
      Referenceadded
      —
      https://git.kernel.org/stable/c/427ab81a811dab4bca9d19f82eec5847ae42646e
      Referenceadded
      —
      https://git.kernel.org/stable/c/6c344fff2feff9d4d716d8e4ad40e9b5040ee5ea
      Referenceadded
      —
      https://git.kernel.org/stable/c/76b94cbd32aacf36a641956385a852635c6802b9
      Referenceadded
      —
      https://git.kernel.org/stable/c/c8e4e0c701d0192a2efb6df059c0f9e19678c23d
      Referenceremoved
      https://git.kernel.org/stable/c/012d37a568bfbb2c9686f03ade75560bc7139956
      —
      Referenceremoved
      https://git.kernel.org/stable/c/30aae62e50b4e074a90a9a5e15246548fbdc1182
      —
      Referenceremoved
      https://git.kernel.org/stable/c/41fe0f7b84f0cb822ae10ab08592996a592b2a25
      —
      Referenceremoved
      https://git.kernel.org/stable/c/427ab81a811dab4bca9d19f82eec5847ae42646e
      —
      Referenceremoved
      https://git.kernel.org/stable/c/6c344fff2feff9d4d716d8e4ad40e9b5040ee5ea
      —
      Referenceremoved
      https://git.kernel.org/stable/c/76b94cbd32aacf36a641956385a852635c6802b9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/c8e4e0c701d0192a2efb6df059c0f9e19678c23d
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/012d37a568bfbb2c9686f03ade75560bc7139956 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/30aae62e50b4e074a90a9a5e15246548fbdc1182 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/41fe0f7b84f0cb822ae10ab08592996a592b2a25 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/427ab81a811dab4bca9d19f82eec5847ae42646e Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/6c344fff2feff9d4d716d8e4ad40e9b5040ee5ea Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/76b94cbd32aacf36a641956385a852635c6802b9 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/c8e4e0c701d0192a2efb6df059c0f9e19678c23d 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-2026-53391","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:30:09.630598Z"}

      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 9 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/pNFS: reject zero-length r_addr in nfs4_decode_mp_ds_addr nfs4_decode_mp_ds_addr() decodes the r_netid and r_addr opaques of a netaddr4 from a GETDEVICEINFO multipath-DS body, then immediately calls strrchr(buf, '.') to locate the port separator. Both decodes use xdr_stream_decode_string_dup(), and the current code checks only "nlen < 0" / "rlen < 0" before dereferencing the returned string. When the on-wire opaque has length zero, xdr_stream_decode_opaque_inline() returns 0 and xdr_stream_decode_string_dup() falls through to its "*str = NULL; return ret" tail, leaving buf NULL with a return value of 0. The "< 0" check does not catch this, and the next line is strrchr(NULL, '.'), a kernel NULL pointer dereference reachable from any pNFS-flexfile client mounted against a malicious or compromised metadata server. Reject the zero-length cases explicitly so the decoder fails with -EBADMSG (treated as a malformed GETDEVICEINFO body) instead of panicking the client.
      Referenceadded
      —
      https://git.kernel.org/stable/c/012d37a568bfbb2c9686f03ade75560bc7139956
      Referenceadded
      —
      https://git.kernel.org/stable/c/30aae62e50b4e074a90a9a5e15246548fbdc1182
      Referenceadded
      —
      https://git.kernel.org/stable/c/41fe0f7b84f0cb822ae10ab08592996a592b2a25
      Referenceadded
      —
      https://git.kernel.org/stable/c/427ab81a811dab4bca9d19f82eec5847ae42646e
      Referenceadded
      —
      https://git.kernel.org/stable/c/6c344fff2feff9d4d716d8e4ad40e9b5040ee5ea
      Referenceadded
      —
      https://git.kernel.org/stable/c/76b94cbd32aacf36a641956385a852635c6802b9
      Referenceadded
      —
      https://git.kernel.org/stable/c/c8e4e0c701d0192a2efb6df059c0f9e19678c23d

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

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