CriticalCVE-2026-63886

    Linux Kernel: Heap-based Buffer Overflow (CVE-2026-63886)

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

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    What is affected, what to do

    A flaw was found in the Linux kernel's iSCSI target functionality. This vulnerability allows a remote attacker to cause a buffer overflow by sending a specially crafted Challenge-Handshake Authentication Authentication Protocol (CHAP) response.

    Update Linux Kernel to version 6.1.176, Linux Kernel to version 6.6.143, Linux Kernel to version 6.12.93.

    Affected
    • Linux Kernel lt 6.0..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 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

    9.8

    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, Red Hat, CVE.org, BSI

    0.7 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 53.6

    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
    92.71 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
    53.6
    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-787, CWE-122

    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 iSCSI target functionality. This vulnerability allows a remote attacker to cause a buffer overflow by sending a specially crafted Challenge-Handshake Authentication Authentication Protocol (CHAP) response. The system fails to validate the length of the BASE64-encoded CHAP response before decoding it, leading to memory corruption. This could potentially lead to a denial of service or other unpredictable system behavior.

    Source: suse_csaf, Ubuntu Security Notices, redhat_csaf, 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
    • 6.13 – < 6.18.35
    • 6.7 – < 6.12.93
    • 6.19 – < 7.0.12
    • 6.0 – < 6.1.176
    • —
    • 6.2 – < 6.6.143
    • 6.18.35
    • 6.12.93
    • 7.0.12
    • 6.1.176
    • 7.1
    • 6.6.143
    IBMQRadar SIEM
    • < 7.6.0.3
    • <7.5.0 UP16 IF01
    • 7.6.0.3
    • —

    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-ibm-6.8jammy
    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—

    Weakness classes (CWE)

    • CWE-787Out-of-bounds Write

      Base

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

      Entry at MITRE CWE-787

    • CWE-122Heap-based Buffer Overflow

      Variant

      A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

      Entry at MITRE CWE-122

    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 (6.13 – before 6.18.35; 6.2 – before 6.6.143; 6.7 – before 6.12.93; 6.0 – before 6.1.176; 6.19 – before 7.0.12; 5 individual versions)

      Weakness type: CWE-787

      Show 8 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-787
      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) 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) 6.0 up to (excluding) 6.1.176 *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
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/4a3a19c98a8207ad08bec554703d90f2c34a8cc6 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/82454e6f21e56ea9a0a9de7d0ff7e1dfb83e34d6 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/85db7391310b1304d2dc8ae3b0b12105a9567147 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/bf154c657828ed05399bca5d98cf1611bb048b12 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/c04e85799356120209b351a148ac2db888d5ffd9 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/edd06675a02376ea8347dba7c29ad982ba5b36ee Types: Patch

      Source identifier: nvd@nist.gov

    2. Record modifiedCISA ADP

      Weakness type: CWE-122

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-122

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

    3. Record modifiedLinux

      Show 12 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/4a3a19c98a8207ad08bec554703d90f2c34a8cc6
      Referenceadded
      —
      https://git.kernel.org/stable/c/82454e6f21e56ea9a0a9de7d0ff7e1dfb83e34d6
      Referenceadded
      —
      https://git.kernel.org/stable/c/85db7391310b1304d2dc8ae3b0b12105a9567147
      Referenceadded
      —
      https://git.kernel.org/stable/c/bf154c657828ed05399bca5d98cf1611bb048b12
      Referenceadded
      —
      https://git.kernel.org/stable/c/c04e85799356120209b351a148ac2db888d5ffd9
      Referenceadded
      —
      https://git.kernel.org/stable/c/edd06675a02376ea8347dba7c29ad982ba5b36ee
      Referenceremoved
      https://git.kernel.org/stable/c/4a3a19c98a8207ad08bec554703d90f2c34a8cc6
      —
      Referenceremoved
      https://git.kernel.org/stable/c/82454e6f21e56ea9a0a9de7d0ff7e1dfb83e34d6
      —
      Referenceremoved
      https://git.kernel.org/stable/c/85db7391310b1304d2dc8ae3b0b12105a9567147
      —
      Referenceremoved
      https://git.kernel.org/stable/c/bf154c657828ed05399bca5d98cf1611bb048b12
      —
      Referenceremoved
      https://git.kernel.org/stable/c/c04e85799356120209b351a148ac2db888d5ffd9
      —
      Referenceremoved
      https://git.kernel.org/stable/c/edd06675a02376ea8347dba7c29ad982ba5b36ee
      —

      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-2026-63886","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:32:54.597243Z"}

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

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