MediumCVE-2026-43085

    Linux Kernel: security vulnerability (CVE-2026-43085)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_log: initialize nfgenmsg in NLMSG_DONE terminator When batching multiple NFLOG messages (inst->qlen > 1), __nfulnl_send() appends an NLMSG_DONE terminator with sizeof(struct nfgenmsg) payload via nlmsg_put(), but never initializes the nfgenmsg bytes. The nlmsg_put() helper only zeroes alignment padding after the payload, not the payload itself, so four bytes of stale kernel heap data are leaked to userspace in the NLMSG_DONE message body.

    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 2.6.23..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..6.12.83
    • Linux Kernel lt 6.13..6.18.24
    • Linux Kernel lt 6.19..6.19.14
    • 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 6.12.83
    • Linux Kernel 6.18.24
    • Linux Kernel 6.19.14
    • Linux Kernel 7.0

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

    Metrics

    5.5

    Priority

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

    Source: NVD, CVSS v3

    5.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.5

    Show all metrics
    Severity
    Medium
    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
    44.55 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
    5.5 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
    5.5
    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
    0.1 %
    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
    2.5
    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

    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
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    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: netfilter: nfnetlink_log: initialize nfgenmsg in NLMSG_DONE terminator When batching multiple NFLOG messages (inst->qlen > 1), __nfulnl_send() appends an NLMSG_DONE terminator with sizeof(struct nfgenmsg) payload via nlmsg_put(), but never initializes the nfgenmsg bytes. The nlmsg_put() helper only zeroes alignment padding after the payload, not the payload itself, so four bytes of stale kernel heap data are leaked to userspace in the NLMSG_DONE message body. Use nfnl_msg_put() to build the NLMSG_DONE terminator, which initializes the nfgenmsg payload via nfnl_fill_hdr(), consistent with how __build_packet_message() already constructs NFULNL_MSG_PACKET headers.

    Source: siemens_advisory, Debian LTS Advisories, suse_csaf, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), ENISA EUVD, 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 – < 6.1.175
    • 6.2 – < 6.6.136
    • 6.19 – < 6.19.14
    • 2.6.23 – < 5.10.258
    • 5.11 – < 5.15.209
    • 6.13 – < 6.18.24
    • 6.7 – < 6.12.83
    • 6.20 – < 7.0
    • 6.1.175
    • 6.6.136
    • 6.19.14
    • 5.10.258
    • 5.15.209
    • 6.18.24
    • 6.12.83
    • 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
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel2.6.23
    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 modifiedSiemens ADP

      Show 3 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-2026-43085.json">CVE-2026-43085</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

    2. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/15d209bccf9273b4a8b4e579ba0e92d065b6ec8c
      Referenceadded
      —
      https://git.kernel.org/stable/c/1f3083aec8836213da441270cdb1ab612dd82cf4
      Referenceadded
      —
      https://git.kernel.org/stable/c/296f18e1c3a87c915a92ed27832d5040a22d1072
      Referenceadded
      —
      https://git.kernel.org/stable/c/368c22aea490f6f50df831b4f9e3623787686c5b
      Referenceadded
      —
      https://git.kernel.org/stable/c/57cc509d82b46150a11dcecc8b25eaa177eda34d
      Referenceadded
      —
      https://git.kernel.org/stable/c/9e2182865de781c41ab16b7985e9d26dcefea867
      Referenceadded
      —
      https://git.kernel.org/stable/c/d1399632ba255d2e02c757af5d9f5d9279ce168c
      Referenceadded
      —
      https://git.kernel.org/stable/c/d552bcfca323d175664d7444989b04f55666978a
      Referenceremoved
      https://git.kernel.org/stable/c/15d209bccf9273b4a8b4e579ba0e92d065b6ec8c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/1f3083aec8836213da441270cdb1ab612dd82cf4
      —
      Referenceremoved
      https://git.kernel.org/stable/c/296f18e1c3a87c915a92ed27832d5040a22d1072
      —
      Referenceremoved
      https://git.kernel.org/stable/c/368c22aea490f6f50df831b4f9e3623787686c5b
      —
      Referenceremoved
      https://git.kernel.org/stable/c/57cc509d82b46150a11dcecc8b25eaa177eda34d
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9e2182865de781c41ab16b7985e9d26dcefea867
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d1399632ba255d2e02c757af5d9f5d9279ce168c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d552bcfca323d175664d7444989b04f55666978a
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/15d209bccf9273b4a8b4e579ba0e92d065b6ec8c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/1f3083aec8836213da441270cdb1ab612dd82cf4 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/296f18e1c3a87c915a92ed27832d5040a22d1072 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/368c22aea490f6f50df831b4f9e3623787686c5b Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/57cc509d82b46150a11dcecc8b25eaa177eda34d Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/9e2182865de781c41ab16b7985e9d26dcefea867 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d1399632ba255d2e02c757af5d9f5d9279ce168c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d552bcfca323d175664d7444989b04f55666978a Types: Patch
      —

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

    3. 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/2026/43xxx/CVE-2026-43085.json">CVE-2026-43085</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html

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

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