CriticalCVE-2026-63992

    Linux Kernel: security vulnerability (CVE-2026-63992)

    Published Last modified Sources: SUSE, Ubuntu, Red Hat, CVE.org, BSI

    What is affected, what to do

    A flaw was found in the Linux kernel's `tunnels` module. This vulnerability occurs when the `iptunnel_pmtud_check_icmp()` function is called without the `skb transport header` being properly set.

    Update Linux Kernel to version 5.10.259, Linux Kernel to version 5.15.210, Linux Kernel to version 6.1.176.

    Affected
    • Linux Kernel lt 5.9..5.10.259
    • Linux Kernel lt 5.11..5.15.210
    • Linux Kernel lt 5.16..6.1.176
    • Linux Kernel lt 6.2..6.6.143
    • Linux Kernel lt 6.7..6.12.93
    • Linux Kernel lt 6.13..6.18.35
    • Linux Kernel lt 6.19..7.0.12
    Fixed in
    • Linux Kernel 5.10.259
    • Linux Kernel 5.15.210
    • Linux Kernel 6.1.176
    • Linux Kernel 6.6.143
    • Linux Kernel 6.12.93
    • Linux Kernel 6.18.35
    • Linux Kernel 7.0.12
    • Linux Kernel 7.1

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

    Metrics

    9.1

    Priority

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

    Source: NVD, CVSS v3

    9.1

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: SUSE, Ubuntu, Red Hat, CVE.org, BSI

    0.5 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 43.7

    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
    81.85 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
    9.1 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
    9.1
    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
    0.5 %
    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
    43.7
    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

    A flaw was found in the Linux kernel's `tunnels` module. This vulnerability occurs when the `iptunnel_pmtud_check_icmp()` function is called without the `skb transport header` being properly set. An attacker could exploit this condition to trigger an out-of-bound memory access, which may lead to system instability or a denial of service.

    Source: suse_csaf, Ubuntu Security Notices, redhat_csaf, NVD (NIST), cvelistv5, 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
    • 6.13 – < 6.18.35
    • 6.7 – < 6.12.93
    • 5.11 – < 5.15.210
    • 6.19 – < 7.0.12
    • 5.9 – < 5.10.259
    • —
    • 5.16 – < 6.1.176
    • 6.2 – < 6.6.143
    • 6.18.35
    • 6.12.93
    • 5.15.210
    • 7.0.12
    • 5.10.259
    • 7.1
    • 6.1.176
    • 6.6.143

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxubuntulinuxnoble
    Linuxubuntulinux-azurenoble
    Linuxubuntulinux-azure-6.8jammy
    Linuxubuntulinux-azure-fdenoble
    Linuxubuntulinux-azure-fde-6.8jammy
    Linuxubuntulinux-azure-fipsnoble
    Linuxubuntulinux-fipsnoble
    Linuxubuntulinux-gcpnoble
    Linuxubuntulinux-gcp-6.8jammy
    Linuxubuntulinux-gcp-fipsnoble
    Linuxubuntulinux-gkenoble
    Linuxubuntulinux-gkeopnoble
    Linuxubuntulinux-ibmnoble
    Linuxubuntulinux-lowlatencynoble
    Linuxubuntulinux-lowlatency-hwe-6.8jammy
    Linuxubuntulinux-oraclenoble
    Linuxubuntulinux-oracle-6.8jammy
    Linuxubuntulinux-raspinoble
    Linuxubuntulinux-raspi-realtimenoble
    Linuxubuntulinux-realtimenoble
    Linuxubuntulinux-realtime-6.8jammy
    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 modifiedCISA ADP

      Weakness type: CWE-125

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-125

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

    2. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93
      Referenceadded
      —
      https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d
      Referenceadded
      —
      https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c
      Referenceadded
      —
      https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4
      Referenceadded
      —
      https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7
      Referenceadded
      —
      https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e
      Referenceadded
      —
      https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c
      Referenceadded
      —
      https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec
      Referenceremoved
      https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93
      —
      Referenceremoved
      https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4
      —
      Referenceremoved
      https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7
      —
      Referenceremoved
      https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e
      —
      Referenceremoved
      https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec Types: Patch
      —

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

    3. 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-2026-63992","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:34:46.388136Z"}

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

    4. Initial analysis by NVDNVD

      Newly listed as affected:
      • Linux Kernel (5.16 – before 6.1.176; 6.13 – before 6.18.35; 6.2 – before 6.6.143; 6.7 – before 6.12.93; 5.11 – before 5.15.210; 6.19 – before 7.0.12; 5.9 – before 5.10.259; 5 individual versions)

      Weakness type: CWE-125

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-125
      Product configurationadded
      —
      OR *cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.16 up to (excluding) 6.1.176 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.18.35 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.2 up to (excluding) 6.6.143 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.12.93 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.11 up to (excluding) 5.15.210 *cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.12 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.9 up to (excluding) 5.10.259
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec Types: Patch

      Source identifier: nvd@nist.gov

    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-2026-63992
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-63992"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-63992.svg?lang=en" alt="CVE-2026-63992 – NEOSEC Intel" height="20"></a>