CriticalCVE-2026-63887

    Linux Kernel: Heap-based Buffer Overflow (CVE-2026-63887)

    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 iSCSI (Internet Small Computer System Interface) target functionality. This vulnerability, a heap overrun, occurs because the iscsi_encode_text_output() function does not properly check buffer capacity when processing login requests.

    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 3.1..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

    9.8

    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

    0.8 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 55.9

    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
    94.79 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
    0.8 %
    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
    55.9
    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-120, 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 (Internet Small Computer System Interface) target functionality. This vulnerability, a heap overrun, occurs because the iscsi_encode_text_output() function does not properly check buffer capacity when processing login requests. A remote attacker could exploit this by sending a specially crafted login request with numerous key-value pairs, leading to a memory corruption issue and potentially a denial of service (DoS) on the system.

    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
    • 3.1 – < 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
    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-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-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

      Base

      The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

      Entry at MITRE CWE-120

    • 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 (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; 3.1 – before 5.10.259; 5 individual versions)

      Weakness type: CWE-120

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-120
      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) 3.1 up to (excluding) 5.10.259
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/bf33e01f88388c43e285492a63e539df6ffed64c Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/cb84e974fb172bc71386289f37b78ea679410b39 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/efe633e600a0ac68357206fede21b1ac8178f3b8 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 16 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db
      Referenceadded
      —
      https://git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3
      Referenceadded
      —
      https://git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b
      Referenceadded
      —
      https://git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a
      Referenceadded
      —
      https://git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627
      Referenceadded
      —
      https://git.kernel.org/stable/c/bf33e01f88388c43e285492a63e539df6ffed64c
      Referenceadded
      —
      https://git.kernel.org/stable/c/cb84e974fb172bc71386289f37b78ea679410b39
      Referenceadded
      —
      https://git.kernel.org/stable/c/efe633e600a0ac68357206fede21b1ac8178f3b8
      Referenceremoved
      https://git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db
      —
      Referenceremoved
      https://git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3
      —
      Referenceremoved
      https://git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b
      —
      Referenceremoved
      https://git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627
      —
      Referenceremoved
      https://git.kernel.org/stable/c/bf33e01f88388c43e285492a63e539df6ffed64c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/cb84e974fb172bc71386289f37b78ea679410b39
      —
      Referenceremoved
      https://git.kernel.org/stable/c/efe633e600a0ac68357206fede21b1ac8178f3b8
      —

      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-2026-63887","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:32:57.099055Z"}

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

    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-2026-63887
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-63887"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-63887.svg?lang=en" alt="CVE-2026-63887 – NEOSEC Intel" height="20"></a>