HighCVE-2025-21727

    Linux Kernel: Use-After-Free (CVE-2025-21727)

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

    What is affected, what to do

    A use-after-free vulnerability was found in the Linux kernel's padata subsystem, in the `padata_reorder()` function. Caused by improper synchronization controls, this vulnerability can occur when a reference-counted data structure (`pd`) is decremented in one thread, freeing it, while another thread still holds a pointer to it and attempts to access it via `padata_find_next()`.

    Update Linux Kernel to version 5.10.235, Linux Kernel to version 5.15.179, Linux Kernel to version 6.1.129.

    Affected
    • Linux Kernel lt 5.4..5.10.235
    • Linux Kernel lt 5.11..5.15.179
    • Linux Kernel lt 5.16..6.1.129
    • Linux Kernel lt 6.2..6.6.76
    • Linux Kernel lt 6.7..6.12.13
    • Linux Kernel lt 6.13..6.13.2
    Fixed in
    • Linux Kernel 5.10.235
    • Linux Kernel 5.15.179
    • Linux Kernel 6.1.129
    • Linux Kernel 6.6.76
    • Linux Kernel 6.12.13
    • Linux Kernel 6.13.2
    • Linux Kernel 6.14

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    7.8

    Priority

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

    Source: NVD, CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: Siemens ProductCERT, Ubuntu, BSI, SUSE, Debian LTS, Red Hat, CVE.org, Msrc Update Guide, EUVD

    0.2 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 12.9

    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
    48.33 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
    7.8 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
    7.8
    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
    0.2 %
    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
    12.9
    Elevated — this CVE ranks above at least 10% of all CVEs scored today.
    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 · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 27 February 2025
    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 use-after-free vulnerability was found in the Linux kernel's padata subsystem, in the `padata_reorder()` function. Caused by improper synchronization controls, this vulnerability can occur when a reference-counted data structure (`pd`) is decremented in one thread, freeing it, while another thread still holds a pointer to it and attempts to access it via `padata_find_next()`. This vulnerability can lead to system instability, denial of service, and potential privilege escalation.

    Source: siemens_advisory, Ubuntu Security Notices, BSI CSAF, BSI WID Portal, suse_csaf, Debian LTS Advisories, redhat_csaf, cvelistv5, NVD (NIST), Microsoft Security Update Guide, CVE.org (MITRE), ENISA EUVD

    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 – < 6.13.2
    • —
    • 5.16 – < 6.1.129
    • 5.11 – < 5.15.179
    • 5.4 – < 5.10.235
    • 6.7 – < 6.12.13
    • 6.2 – < 6.6.76
    • 6.13.2
    • 6.14
    • 6.1.129
    • 5.15.179
    • 5.10.235
    • 6.12.13
    • 6.6.76
    DellSecure Connect Gateway
    • < 5.30.0.14
    • 5.30.0.14
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxubuntuawsbionic
    Linuxubuntuawsjammy
    Linuxubuntuawsnoble
    Linuxubuntuawsresolute
    Linuxubuntuawsxenial
    Linuxubuntuaws-6.8jammy
    Linuxubuntuaws-hwexenial
    Linuxubuntuazurejammy
    Linuxubuntuazurenoble
    Linuxubuntuazureresolute
    Linuxubuntuazurexenial
    Linuxubuntuazure-4.15bionic
    Linuxubuntugcpjammy
    Linuxubuntugcpnoble
    Linuxubuntugcpresolute
    Linuxubuntugcpxenial
    Linuxubuntugcp-4.15bionic
    Linuxubuntugcp-6.8jammy
    Linuxubuntugeneric-4.15bionic
    Linuxubuntugeneric-4.15xenial
    Linuxubuntugeneric-4.4xenial
    Linuxubuntugeneric-5.4bionic
    Linuxubuntugeneric-5.4focal
    Linuxubuntugkejammy

    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 modifiedLinux

      CVSS V3.1: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

      Show 22 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
      Referenceadded
      —
      https://git.kernel.org/stable/c/0ae2f332cfd2d74cf3ce344ec9938cf3e29c3ccd
      Referenceadded
      —
      https://git.kernel.org/stable/c/573ac9c70bf7885dc85d82fa44550581bfc3b738
      Referenceadded
      —
      https://git.kernel.org/stable/c/80231f069240d52e98b6a317456c67b2eafd0781
      Referenceadded
      —
      https://git.kernel.org/stable/c/bbccae982e9fa1d7abcb23a5ec81cb0ec883f7de
      Referenceadded
      —
      https://git.kernel.org/stable/c/e01780ea4661172734118d2a5f41bc9720765668
      Referenceadded
      —
      https://git.kernel.org/stable/c/f3e0b9f790f8e8065d59e67b565a83154d9f3079
      Referenceadded
      —
      https://git.kernel.org/stable/c/f78170bee51469734b1a306a74fc5f777bb22ba6
      Referenceremoved
      https://git.kernel.org/stable/c/0ae2f332cfd2d74cf3ce344ec9938cf3e29c3ccd
      —
      Referenceremoved
      https://git.kernel.org/stable/c/573ac9c70bf7885dc85d82fa44550581bfc3b738
      —
      Referenceremoved
      https://git.kernel.org/stable/c/80231f069240d52e98b6a317456c67b2eafd0781
      —
      Referenceremoved
      https://git.kernel.org/stable/c/bbccae982e9fa1d7abcb23a5ec81cb0ec883f7de
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e01780ea4661172734118d2a5f41bc9720765668
      —
      Referenceremoved
      https://git.kernel.org/stable/c/f3e0b9f790f8e8065d59e67b565a83154d9f3079
      —
      Referenceremoved
      https://git.kernel.org/stable/c/f78170bee51469734b1a306a74fc5f777bb22ba6
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/0ae2f332cfd2d74cf3ce344ec9938cf3e29c3ccd Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/573ac9c70bf7885dc85d82fa44550581bfc3b738 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/80231f069240d52e98b6a317456c67b2eafd0781 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/bbccae982e9fa1d7abcb23a5ec81cb0ec883f7de Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e01780ea4661172734118d2a5f41bc9720765668 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/f3e0b9f790f8e8065d59e67b565a83154d9f3079 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/f78170bee51469734b1a306a74fc5f777bb22ba6 Types: Patch
      —

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

    2. Record modifiedCVE Program

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
      Referenceadded
      —
      https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
      Referenceremoved
      https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
      —
      Referenceremoved
      https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
      —

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

    3. Record modifiedSiemens ADP

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2025/21xxx/CVE-2025-21727.json">CVE-2025-21727</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-265688.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-265688.html
      —

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

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