MediumCVE-2026-45844

    Linux Kernel: security vulnerability (CVE-2026-45844)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: netfilter: arp_tables: fix IEEE1394 ARP payload parsing Weiming Shi says: "arp_packet_match() unconditionally parses the ARP payload assuming two hardware addresses are present (source and target). However, IPv4-over-IEEE1394 ARP (RFC 2734) omits the target hardware address field, and arp_hdr_len() already accounts for this by returning a shorter length for ARPHRD_IEEE1394 devices.

    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 3.10..5.10.258
    • Linux Kernel lt 5.11..5.15.209
    • Linux Kernel lt 5.16..6.1.175
    • Linux Kernel lt 6.2..6.6.141
    • Linux Kernel lt 6.7..6.12.91
    • Linux Kernel lt 6.13..6.18.33
    • Linux Kernel lt 6.19..7.0.10
    Fixed in
    • Linux Kernel 5.10.258
    • Linux Kernel 5.15.209
    • Linux Kernel 6.1.175
    • Linux Kernel 6.6.141
    • Linux Kernel 6.12.91
    • Linux Kernel 6.18.33
    • Linux Kernel 7.0.10
    • Linux Kernel 7.1

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.8

    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
    45.57 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
    2.8
    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: arp_tables: fix IEEE1394 ARP payload parsing Weiming Shi says: "arp_packet_match() unconditionally parses the ARP payload assuming two hardware addresses are present (source and target). However, IPv4-over-IEEE1394 ARP (RFC 2734) omits the target hardware address field, and arp_hdr_len() already accounts for this by returning a shorter length for ARPHRD_IEEE1394 devices. As a result, on IEEE1394 interfaces arp_packet_match() advances past a nonexistent target hardware address and reads the wrong bytes for both the target device address comparison and the target IP address. This causes arptables rules to match against garbage data, leading to incorrect filtering decisions: packets that should be accepted may be dropped and vice versa. The ARP stack in net/ipv4/arp.c (arp_create and arp_process) already handles this correctly by skipping the target hardware address for ARPHRD_IEEE1394. Apply the same pattern to arp_packet_match()." Mangle the original patch to always return 0 (no match) in case user matches on the target hardware address which is never present in IEEE1394. Note that this returns 0 (no match) for either normal and inverse match because matching in the target hardware address in ARPHRD_IEEE1394 has never been supported by arptables. This is intentional, matching on the target hardware address should never evaluate true for ARPHRD_IEEE1394. Moreover, adjust arpt_mangle to drop the packet too as AI suggests: In arpt_mangle, the logic assumes a standard ARP layout. Because IEEE1394 (FireWire) omits the target hardware address, the linear pointer arithmetic miscalculates the offset for the target IP address. This causes mangling operations to write to the wrong location, leading to packet corruption. To ensure safety, this patch drops packets (NF_DROP) when mangling is requested for these fields on IEEE1394 devices, as the current implementation cannot correctly map the FireWire ARP payload. This omits both mangling target hardware and IP address. Even if IP address mangling should be possible in IEEE1394, this would require to adjust arpt_mangle offset calculation, which has never been supported. Based on patch from Weiming Shi <bestswngs@gmail.com>.

    Source: Debian LTS Advisories, Ubuntu Security Notices, siemens_advisory, Debian Security Advisories, BSI WID Portal, BSI CSAF, NVD (NIST), CVE.org (MITRE), cvelistv5, Microsoft Security Update Guide, 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
    • 5.16 – < 6.1.175
    • 5.11 – < 5.15.209
    • 3.10 – < 5.10.258
    • 6.7 – < 6.12.91
    • —
    • 6.13 – < 6.18.33
    • 6.2 – < 6.6.141
    • 6.19 – < 7.0.10
    • 6.1.175
    • 5.15.209
    • 5.10.258
    • 6.12.91
    • 7.1
    • 6.18.33
    • 6.6.141
    • 7.0.10
    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
    Linuxubuntulinux-oracle-7.0noble
    Linuxlinuxlinux_kernel7.1
    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 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
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      https://git.kernel.org/stable/c/03ea11dbefaa55c502735ee551c89ef773fe753b
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      https://git.kernel.org/stable/c/0f23a1457695f1a61f64367e39f0f9cfa29947d1
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      https://git.kernel.org/stable/c/1c55053f8ffdc060006df898fd3664e3d1bfac7b
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      https://git.kernel.org/stable/c/1e285362ef7096eb12733370d59e033f4a1d294a
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      https://git.kernel.org/stable/c/1e8e3f449b1e73b73a843257635b9c50f0cc0f0a
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      https://git.kernel.org/stable/c/84e8536c981338d0d8cc6e712cf71a936a93e13f
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      https://git.kernel.org/stable/c/ac698d81fd6619c7504cee913f1cab5285fba1b7
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      https://git.kernel.org/stable/c/ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b
      Referenceremoved
      https://git.kernel.org/stable/c/03ea11dbefaa55c502735ee551c89ef773fe753b
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      https://git.kernel.org/stable/c/0f23a1457695f1a61f64367e39f0f9cfa29947d1
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      https://git.kernel.org/stable/c/1c55053f8ffdc060006df898fd3664e3d1bfac7b
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      https://git.kernel.org/stable/c/1e285362ef7096eb12733370d59e033f4a1d294a
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      https://git.kernel.org/stable/c/1e8e3f449b1e73b73a843257635b9c50f0cc0f0a
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      Referenceremoved
      https://git.kernel.org/stable/c/84e8536c981338d0d8cc6e712cf71a936a93e13f
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      https://git.kernel.org/stable/c/ac698d81fd6619c7504cee913f1cab5285fba1b7
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      https://git.kernel.org/stable/c/ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b
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      Reference typeremoved
      https://git.kernel.org/stable/c/03ea11dbefaa55c502735ee551c89ef773fe753b Types: Patch
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      Reference typeremoved
      https://git.kernel.org/stable/c/0f23a1457695f1a61f64367e39f0f9cfa29947d1 Types: Patch
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      Reference typeremoved
      https://git.kernel.org/stable/c/1c55053f8ffdc060006df898fd3664e3d1bfac7b Types: Patch
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      Reference typeremoved
      https://git.kernel.org/stable/c/1e285362ef7096eb12733370d59e033f4a1d294a Types: Patch
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      https://git.kernel.org/stable/c/1e8e3f449b1e73b73a843257635b9c50f0cc0f0a Types: Patch
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      Reference typeremoved
      https://git.kernel.org/stable/c/84e8536c981338d0d8cc6e712cf71a936a93e13f Types: Patch
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      Reference typeremoved
      https://git.kernel.org/stable/c/ac698d81fd6619c7504cee913f1cab5285fba1b7 Types: Patch
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      Reference typeremoved
      https://git.kernel.org/stable/c/ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b Types: Patch
      —

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

    2. 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/2026/45xxx/CVE-2026-45844.json">CVE-2026-45844</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

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