HighCVE-2026-23444

    Linux Kernel: Double Free (CVE-2026-23444)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: always free skb on ieee80211_tx_prepare_skb() failure ieee80211_tx_prepare_skb() has three error paths, but only two of them free the skb. The first error path (ieee80211_tx_prepare() returning TX_DROP) does not free it, while invoke_tx_handlers() failure and the fragmentation check both do.

    Update Linux Kernel to version 5.10.258, Linux Kernel to version 5.15.209, Linux Kernel to version 6.1.175.

    Affected
    • Linux Kernel lt 3.13..5.10.258
    • Linux Kernel lt 5.11..5.15.209
    • Linux Kernel lt 5.16..6.1.175
    • Linux Kernel lt 6.2..6.6.136
    • Linux Kernel lt 6.7..6.12.84
    • 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 5.10.258
    • Linux Kernel 5.15.209
    • Linux Kernel 6.1.175
    • Linux Kernel 6.6.136
    • Linux Kernel 6.12.84
    • 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

    7.8

    Priority

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

    Source: Vendor (CNA), CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 3.0

    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
    54.90 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
    0.1 %
    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
    3.0
    Low — this CVE sits in the lower 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 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

    In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: always free skb on ieee80211_tx_prepare_skb() failure ieee80211_tx_prepare_skb() has three error paths, but only two of them free the skb. The first error path (ieee80211_tx_prepare() returning TX_DROP) does not free it, while invoke_tx_handlers() failure and the fragmentation check both do. Add kfree_skb() to the first error path so all three are consistent, and remove the now-redundant frees in callers (ath9k, mt76, mac80211_hwsim) to avoid double-free. Document the skb ownership guarantee in the function's kdoc.

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

    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 – < 6.1.175
    • 6.2 – < 6.6.136
    • 3.13 – < 5.10.258
    • 6.7 – < 6.12.84
    • 5.11 – < 5.15.209
    • 6.19 – < 6.19.10
    • 6.13 – < 6.18.20
    • 6.20 – < 7.0
    • 6.1.175
    • 6.6.136
    • 5.10.258
    • 6.12.84
    • 5.15.209
    • 6.19.10
    • 6.18.20
    • 7.0
    MicrosoftAzure Linux
    • azl3
    • —
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinuxtrixie
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel3.13
    Linuxlinuxlinux_kernel7.0
    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 modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-23444","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:08:09.371784Z"}

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

    3. Record modifiedLinux

      Show 19 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/06e769dddcbeb3baf2ce346273b53dd61fdbecf4
      Referenceadded
      —
      https://git.kernel.org/stable/c/3b4d27acafaeab478fd24f79ad6e593a892828b9
      Referenceadded
      —
      https://git.kernel.org/stable/c/50f1b690b4868923fbd242298def2fb88662f108
      Referenceadded
      —
      https://git.kernel.org/stable/c/5ef8ca1c164786da24169af155c1ca1ff1353cf8
      Referenceadded
      —
      https://git.kernel.org/stable/c/905ef207d5ed99ca64adfe39fba9ac46e434327a
      Referenceadded
      —
      https://git.kernel.org/stable/c/9a779d1f480e83720b5384adf165604e7ee226bd
      Referenceadded
      —
      https://git.kernel.org/stable/c/d5ad6ab61cbd89afdb60881f6274f74328af3ee9
      Referenceadded
      —
      https://git.kernel.org/stable/c/f77b51bcee7be2bb686b5f7a2d4a1921e4bdb9f4
      Referenceremoved
      https://git.kernel.org/stable/c/06e769dddcbeb3baf2ce346273b53dd61fdbecf4
      —
      Referenceremoved
      https://git.kernel.org/stable/c/3b4d27acafaeab478fd24f79ad6e593a892828b9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/50f1b690b4868923fbd242298def2fb88662f108
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5ef8ca1c164786da24169af155c1ca1ff1353cf8
      —
      Referenceremoved
      https://git.kernel.org/stable/c/905ef207d5ed99ca64adfe39fba9ac46e434327a
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9a779d1f480e83720b5384adf165604e7ee226bd
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d5ad6ab61cbd89afdb60881f6274f74328af3ee9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/f77b51bcee7be2bb686b5f7a2d4a1921e4bdb9f4
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/06e769dddcbeb3baf2ce346273b53dd61fdbecf4 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/50f1b690b4868923fbd242298def2fb88662f108 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d5ad6ab61cbd89afdb60881f6274f74328af3ee9 Types: Patch
      —

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

    4. Record modifiedSiemens ADP

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/23xxx/CVE-2026-23444.json">CVE-2026-23444</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

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