CriticalCVE-2026-63912

    Linux Kernel: Out-of-bounds Read (CVE-2026-63912)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: xfrm: esp: restore combined single-frag length gate The ESP out-of-place fast path appends the trailer in esp_output_head() before esp_output_tail() allocates the destination page frag. The head-side gate currently checks skb->data_len and tailen separately, but the tail code allocates a single destination frag from the combined post-trailer skb->data_len.

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Conflicting version data — version display is hidden until the data is resolved.

    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: SUSE, Ubuntu, CVE.org, BSI

    0.7 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 53.7

    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
    92.98 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
    0.7 %
    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
    53.7
    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
    CISA assessment (SSVC)
    Exploitation: none known · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 16 October 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-125

    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: xfrm: esp: restore combined single-frag length gate The ESP out-of-place fast path appends the trailer in esp_output_head() before esp_output_tail() allocates the destination page frag. The head-side gate currently checks skb->data_len and tailen separately, but the tail code allocates a single destination frag from the combined post-trailer skb->data_len. Reject the page-frag fast path when the combined aligned length exceeds a page. Otherwise skb_page_frag_refill() may fall back to a single page while the destination sg still spans the combined skb->data_len. Restore this combined-length page gate for both IPv4 and IPv6.

    Source: suse_csaf, Ubuntu Security Notices, cvelistv5, NVD (NIST), 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
    • 5.17.5 – < 5.18
    • 5.18 – < 6.1.176
    • 4.14.288 – < 4.15
    • 5.10.113 – < 5.10.259
    • 6.13 – < 6.18.35
    • 6.7 – < 6.12.93
    • 6.19 – < 7.0.12
    • 5.4.205 – < 5.5
    • 4.19.252 – < 4.20
    • 5.15.36 – < 5.15.210
    • —
    • 6.2 – < 6.6.143
    • 5.18
    • 6.1.176
    • 4.15
    • 5.10.259
    • 6.18.35
    • 6.12.93
    • 7.0.12
    • 5.5
    • 4.20
    • 5.15.210
    • 7.1
    • 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_kernel5.18
    Linuxlinuxlinux_kernel7.1
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-125Out-of-bounds Read

      Base

      The product reads data past the end, or before the beginning, of the intended buffer.

      Entry at MITRE CWE-125

    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. Initial analysis by NVDNVD

      Newly listed as affected:
      • Linux Kernel (4.19.252 – before 4.20; 6.13 – before 6.18.35; 6.2 – before 6.6.143; 6.7 – before 6.12.93; 5.18.1 – before 6.1.176; 6.19 – before 7.0.12; 5.4.205 – before 5.5; 4.14.288 – before 4.15; 5.10.113 – before 5.10.259; 5.15.36 – before 5.15.210; 5.17.5 – before 5.18; 10 individual versions)
      Show 9 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *cpe:2.3:o:linux:linux_kernel:5.18:rc7:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.18:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.18:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.18:rc6:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.18:-:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 4.19.252 up to (excluding) 4.20 *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) 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:7.1:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.18.1 up to (excluding) 6.1.176 *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) 5.4.205 up to (excluding) 5.5 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 4.14.288 up to (excluding) 4.15 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.10.113 up to (excluding) 5.10.259 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.15.36 up to (excluding) 5.15.210 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.17.5 up to (excluding) 5.18
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/322e48187e0245ab2fff6fec2220b0cae677dbec Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/36519e3d941fc99d3b52c134dbaf311f987a4708 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/566295735530ee513326049b0540f32ec050bf2e Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/5d7ab86e2b6bc23054616bf6ac562013bf60af8c Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/65f3b3fc2347b89fe21db1e92c7681368415f095 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/b84091ceddc9f133229dceab3ccc930bf27f9cba Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/c093468aea8277f77272a4f199b2e15e19cabb59 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/dfa0d7b0ff1eb6b2c416b8fdb9b4f2cefba57a40 Types: Patch

      Source identifier: nvd@nist.gov

    2. 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

    3. Record modifiedLinux

      Show 16 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/322e48187e0245ab2fff6fec2220b0cae677dbec
      Referenceadded
      —
      https://git.kernel.org/stable/c/36519e3d941fc99d3b52c134dbaf311f987a4708
      Referenceadded
      —
      https://git.kernel.org/stable/c/566295735530ee513326049b0540f32ec050bf2e
      Referenceadded
      —
      https://git.kernel.org/stable/c/5d7ab86e2b6bc23054616bf6ac562013bf60af8c
      Referenceadded
      —
      https://git.kernel.org/stable/c/65f3b3fc2347b89fe21db1e92c7681368415f095
      Referenceadded
      —
      https://git.kernel.org/stable/c/b84091ceddc9f133229dceab3ccc930bf27f9cba
      Referenceadded
      —
      https://git.kernel.org/stable/c/c093468aea8277f77272a4f199b2e15e19cabb59
      Referenceadded
      —
      https://git.kernel.org/stable/c/dfa0d7b0ff1eb6b2c416b8fdb9b4f2cefba57a40
      Referenceremoved
      https://git.kernel.org/stable/c/322e48187e0245ab2fff6fec2220b0cae677dbec
      —
      Referenceremoved
      https://git.kernel.org/stable/c/36519e3d941fc99d3b52c134dbaf311f987a4708
      —
      Referenceremoved
      https://git.kernel.org/stable/c/566295735530ee513326049b0540f32ec050bf2e
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5d7ab86e2b6bc23054616bf6ac562013bf60af8c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/65f3b3fc2347b89fe21db1e92c7681368415f095
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b84091ceddc9f133229dceab3ccc930bf27f9cba
      —
      Referenceremoved
      https://git.kernel.org/stable/c/c093468aea8277f77272a4f199b2e15e19cabb59
      —
      Referenceremoved
      https://git.kernel.org/stable/c/dfa0d7b0ff1eb6b2c416b8fdb9b4f2cefba57a40
      —

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

    4. 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-2026-63912","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:33:08.898705Z"}

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

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