CriticalCVE-2026-43011

    Linux Kernel: Double Free (CVE-2026-43011)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: net/x25: Fix potential double free of skb When alloc_skb fails in x25_queue_rx_frame it calls kfree_skb(skb) at line 48 and returns 1 (error). This error propagates back through the call chain: x25_queue_rx_frame returns 1 | v x25_state3_machine receives the return value 1 and takes the else branch at line 278, setting queued=0 and returning 0 | v x25_process_rx_frame returns queued=0 | v x25_backlog_rcv at line 452 sees queued=0 and calls kfree_skb(skb) again This would free the same skb twice.

    Update Linux Kernel to version 5.10.253, Linux Kernel to version 5.15.203, Linux Kernel to version 6.1.168.

    Affected
    • Linux Kernel lt 2.6.12..5.10.253
    • Linux Kernel lt 5.11..5.15.203
    • Linux Kernel lt 5.16..6.1.168
    • Linux Kernel lt 6.2..6.6.134
    • Linux Kernel lt 6.7..6.12.81
    • Linux Kernel lt 6.13..6.18.22
    • Linux Kernel lt 6.19..6.19.12
    • Linux Kernel lt 6.20..7.0
    Fixed in
    • Linux Kernel 5.10.253
    • Linux Kernel 5.15.203
    • Linux Kernel 6.1.168
    • Linux Kernel 6.6.134
    • Linux Kernel 6.12.81
    • Linux Kernel 6.18.22
    • Linux Kernel 6.19.12
    • Linux Kernel 7.0

    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: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

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

    0.6 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 48.0

    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
    84.38 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
    0.6 %
    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
    48.0
    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

    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: net/x25: Fix potential double free of skb When alloc_skb fails in x25_queue_rx_frame it calls kfree_skb(skb) at line 48 and returns 1 (error). This error propagates back through the call chain: x25_queue_rx_frame returns 1 | v x25_state3_machine receives the return value 1 and takes the else branch at line 278, setting queued=0 and returning 0 | v x25_process_rx_frame returns queued=0 | v x25_backlog_rcv at line 452 sees queued=0 and calls kfree_skb(skb) again This would free the same skb twice. Looking at x25_backlog_rcv: net/x25/x25_in.c:x25_backlog_rcv() { ... queued = x25_process_rx_frame(sk, skb); ... if (!queued) kfree_skb(skb); }

    Source: Debian LTS Advisories, suse_csaf, siemens_advisory, Ubuntu Security Notices, Debian Security Advisories, NVD (NIST), CVE.org (MITRE), cvelistv5, 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
    • 6.19 – < 6.19.12
    • 5.16 – < 6.1.168
    • 6.13 – < 6.18.22
    • 2.6.12 – < 5.10.253
    • 5.11 – < 5.15.203
    • 6.20 – < 7.0
    • 6.7 – < 6.12.81
    • 6.2 – < 6.6.134
    • 6.19.12
    • 6.1.168
    • 6.18.22
    • 5.10.253
    • 5.15.203
    • 7.0
    • 6.12.81
    • 6.6.134
    MicrosoftAzure Linux
    • azl3
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel2.6.12
    Linuxlinuxlinux_kernel7.0
    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 modifiedCISA ADP

      Weakness type: CWE-415

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-415

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

    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-2026-43011","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:13:26.745898Z"}

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

    3. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/143d4fa68ae9efb83b0c55b12cc7f0d03732a2b1
      Referenceadded
      —
      https://git.kernel.org/stable/c/3f5e3005984645bf5bd129c6b13149879580b1fb
      Referenceadded
      —
      https://git.kernel.org/stable/c/524371398d8463ea7e101fce2cbf3915645d1730
      Referenceadded
      —
      https://git.kernel.org/stable/c/5d0aa038a90b30c9bedde0c41c1fdcd98ecb16e9
      Referenceadded
      —
      https://git.kernel.org/stable/c/c87dd137c0dad07cc55f98181ff380b0c23d2878
      Referenceadded
      —
      https://git.kernel.org/stable/c/d10a26aa4d072320530e6968ef945c8c575edf61
      Referenceadded
      —
      https://git.kernel.org/stable/c/f782dd382203b2a8c4552a628431b7de65a19a7b
      Referenceadded
      —
      https://git.kernel.org/stable/c/fa1dbc93530b34fab0da9862426fe9c918c74dc0
      Referenceremoved
      https://git.kernel.org/stable/c/143d4fa68ae9efb83b0c55b12cc7f0d03732a2b1
      —
      Referenceremoved
      https://git.kernel.org/stable/c/3f5e3005984645bf5bd129c6b13149879580b1fb
      —
      Referenceremoved
      https://git.kernel.org/stable/c/524371398d8463ea7e101fce2cbf3915645d1730
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5d0aa038a90b30c9bedde0c41c1fdcd98ecb16e9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/c87dd137c0dad07cc55f98181ff380b0c23d2878
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d10a26aa4d072320530e6968ef945c8c575edf61
      —
      Referenceremoved
      https://git.kernel.org/stable/c/f782dd382203b2a8c4552a628431b7de65a19a7b
      —
      Referenceremoved
      https://git.kernel.org/stable/c/fa1dbc93530b34fab0da9862426fe9c918c74dc0
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/143d4fa68ae9efb83b0c55b12cc7f0d03732a2b1 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/3f5e3005984645bf5bd129c6b13149879580b1fb Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/524371398d8463ea7e101fce2cbf3915645d1730 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/5d0aa038a90b30c9bedde0c41c1fdcd98ecb16e9 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/c87dd137c0dad07cc55f98181ff380b0c23d2878 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d10a26aa4d072320530e6968ef945c8c575edf61 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/f782dd382203b2a8c4552a628431b7de65a19a7b Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/fa1dbc93530b34fab0da9862426fe9c918c74dc0 Types: Patch
      —

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

    4. Record modifiedSiemens ADP

      Show 6 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/2026/43xxx/CVE-2026-43011.json">CVE-2026-43011</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      —
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
      —

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

    Linked advisories

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2026-43011
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-43011"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-43011.svg?lang=en" alt="CVE-2026-43011 – NEOSEC Intel" height="20"></a>