HighCVE-2026-23300

    Linux Kernel: security vulnerability (CVE-2026-23300)

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

    What is affected, what to do

    Update Linux Kernel to version 5.10.253, Linux Kernel to version 5.15.203, Linux Kernel to version 6.1.167.

    Affected
    • Linux Kernel lt 5.3..5.10.253
    • Linux Kernel lt 5.11..5.15.203
    • Linux Kernel lt 5.16..6.1.167
    • Linux Kernel lt 6.2..6.6.130
    • Linux Kernel lt 6.7..6.12.77
    • Linux Kernel lt 6.13..6.18.17
    • Linux Kernel lt 6.19..6.19.7
    • Linux Kernel lt 6.20..7.0
    Fixed in
    • Linux Kernel 5.10.253
    • Linux Kernel 5.15.203
    • Linux Kernel 6.1.167
    • Linux Kernel 6.6.130
    • Linux Kernel 6.12.77
    • Linux Kernel 6.18.17
    • Linux Kernel 6.19.7
    • Linux Kernel 7.0

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

    Metrics

    7.5

    Priority

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

    Source: Vendor (CNA), CVSS v3

    5.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.9

    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
    43.08 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
    7.5 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
    2.9
    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
    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: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop

    When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics.

    Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows:

    1. Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"): RTF_REJECT is set, enters reject path, skips fib_nh_common_init(). No behavior change.

    2. Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. ip6_route_info_create_nh() still promotes it to reject afterward. nhc_pcpu_rth_output is allocated but unused, which is harmless.

    3. Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. nhc_pcpu_rth_output is properly allocated, fixing the crash when IPv4 routes reference this nexthop.

    Source: siemens_advisory, Debian Security Advisories, Debian LTS Advisories, suse_csaf, Ubuntu Security Notices, BSI WID Portal, BSI 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
    • 6.7 – < 6.12.77
    • 6.2 – < 6.6.130
    • 5.3 – < 5.10.253
    • 5.11 – < 5.15.203
    • 6.20 – < 7.0
    • 6.19 – < 6.19.7
    • 6.13 – < 6.18.17
    • 5.16 – < 6.1.167
    • 6.12.77
    • 6.6.130
    • 5.10.253
    • 5.15.203
    • 7.0
    • 6.19.7
    • 6.18.17
    • 6.1.167
    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_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 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/21ec92774d1536f71bdc90b0e3d052eff99cf093
      Referenceadded
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      https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644
      Referenceadded
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      https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133
      Referenceadded
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      https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc
      Referenceadded
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      https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c
      Referenceadded
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      https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a
      Referenceadded
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      https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9
      Referenceadded
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      https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f
      Referenceremoved
      https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093
      —
      Referenceremoved
      https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644
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      Referenceremoved
      https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133
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      Referenceremoved
      https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc
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      Referenceremoved
      https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c
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      Referenceremoved
      https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a
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      Referenceremoved
      https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9
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      Referenceremoved
      https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f Types: Patch
      —

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

    2. Record modifiedSiemens ADP

      Show 7 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/2026/23xxx/CVE-2026-23300.json">CVE-2026-23300</a>
      Referenceadded
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      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      Referenceadded
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      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
      Referenceadded
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      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
      Referenceadded
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      https://cert-portal.siemens.com/productcert/html/ssa-784472.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

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