CriticalCVE-2025-37924

    Linux Kernel: Use-After-Free (CVE-2025-37924)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in kerberos authentication Setting sess->user = NULL was introduced to fix the dangling pointer created by ksmbd_free_user. However, it is possible another thread could be operating on the session and make use of sess->user after it has been passed to ksmbd_free_user but before sess->user is set to NULL.

    Update Linux Kernel to version 6.1.138, Linux Kernel to version 6.6.90, Linux Kernel to version 6.12.28.

    Affected
    • Linux Kernel lt 5.15..6.1.138
    • Linux Kernel lt 6.2..6.6.90
    • Linux Kernel lt 6.7..6.12.28
    • Linux Kernel lt 6.13..6.14.6
    Fixed in
    • Linux Kernel 6.1.138
    • Linux Kernel 6.6.90
    • Linux Kernel 6.12.28
    • Linux Kernel 6.14.6
    • Linux Kernel 6.15

    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: Ubuntu, Debian LTS, Debian, CVE.org, Msrc Update Guide, EUVD, BSI

    24.6 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 97.9

    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
    134.68 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
    24.6 %
    Elevated — model estimates 10-50% 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
    97.9
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    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 15 October 2026

    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: ksmbd: fix use-after-free in kerberos authentication Setting sess->user = NULL was introduced to fix the dangling pointer created by ksmbd_free_user. However, it is possible another thread could be operating on the session and make use of sess->user after it has been passed to ksmbd_free_user but before sess->user is set to NULL.

    Source: Ubuntu Security Notices, Debian LTS Advisories, Debian Security Advisories, cvelistv5, NVD (NIST), Microsoft Security Update Guide, CVE.org (MITRE), ENISA EUVD, 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
    • —
    • 6.13 – < 6.14.6
    • 6.2 – < 6.6.90
    • 6.7 – < 6.12.28
    • 5.15 – < 6.1.138
    • 6.15
    • 6.14.6
    • 6.6.90
    • 6.12.28
    • 6.1.138

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebiandebian_linux11.0
    Linuxdebianlinuxbookworm
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel6.15
    Linuxlinuxlinux_kernel—

    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 modifiedLinux

      Show 15 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/28c756738af44a404a91b77830d017bb0c525890
      Referenceadded
      —
      https://git.kernel.org/stable/c/b447463562238428503cfba1c913261047772f90
      Referenceadded
      —
      https://git.kernel.org/stable/c/e18c616718018dfc440e4a2d2b94e28fe91b1861
      Referenceadded
      —
      https://git.kernel.org/stable/c/e34a33d5d7e87399af0a138bb32f6a3e95dd83d2
      Referenceadded
      —
      https://git.kernel.org/stable/c/e86e9134e1d1c90a960dd57f59ce574d27b9a124
      Referenceremoved
      https://git.kernel.org/stable/c/28c756738af44a404a91b77830d017bb0c525890
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b447463562238428503cfba1c913261047772f90
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e18c616718018dfc440e4a2d2b94e28fe91b1861
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e34a33d5d7e87399af0a138bb32f6a3e95dd83d2
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e86e9134e1d1c90a960dd57f59ce574d27b9a124
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/28c756738af44a404a91b77830d017bb0c525890 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b447463562238428503cfba1c913261047772f90 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e18c616718018dfc440e4a2d2b94e28fe91b1861 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e34a33d5d7e87399af0a138bb32f6a3e95dd83d2 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e86e9134e1d1c90a960dd57f59ce574d27b9a124 Types: Patch
      —

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

    2. 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-2025-37924","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-15T21:46:12.066488Z"}

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

    3. Record modifiedCVE Program

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html
      Referenceremoved
      https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html
      —
      Reference typeremoved
      https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html Types: Mailing List, Third Party Advisory
      —

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

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