HighCVE-2026-23388

    Linux Kernel: Out-of-Bounds Access (CVE-2026-23388)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: Squashfs: check metadata block offset is within range Syzkaller reports a "general protection fault in squashfs_copy_data" This is ultimately caused by a corrupted index look-up table, which produces a negative metadata block offset. This is subsequently passed to squashfs_copy_data (via squashfs_read_metadata) where the negative offset causes an out of bounds access.

    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 2.6.29..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

    7.1

    Priority

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

    Source: NVD, CVSS v3

    7.1

    CVSS v3

    Severity High on the scale from 0 to 10.

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.1

    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
    51.03 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
    7.1 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
    7.1
    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
    0.1 %
    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
    2.1
    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: Squashfs: check metadata block offset is within range Syzkaller reports a "general protection fault in squashfs_copy_data" This is ultimately caused by a corrupted index look-up table, which produces a negative metadata block offset. This is subsequently passed to squashfs_copy_data (via squashfs_read_metadata) where the negative offset causes an out of bounds access. The fix is to check that the offset is within range in squashfs_read_metadata. This will trap this and other cases.

    Source: Debian LTS Advisories, Debian Security Advisories, siemens_advisory, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), Microsoft Security Update Guide, ENISA EUVD, CVE.org (MITRE)

    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
    • 2.6.29 – < 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_kernel2.6.29
    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
      —
      https://git.kernel.org/stable/c/01ee0bcc29864b78249308e8b35042b09bbf5fe3
      Referenceadded
      —
      https://git.kernel.org/stable/c/0c8ab092aec3ac4294940054772d30b511b16713
      Referenceadded
      —
      https://git.kernel.org/stable/c/3b9499e7d677dd4366239a292238489a804936b2
      Referenceadded
      —
      https://git.kernel.org/stable/c/3f68a9457a6190814377577374da75f872e0a013
      Referenceadded
      —
      https://git.kernel.org/stable/c/60f679f643f3f36a8571ea585e4ce5d93ef952b5
      Referenceadded
      —
      https://git.kernel.org/stable/c/6b847d65f5b0065e02080c61fad93d57d6686383
      Referenceadded
      —
      https://git.kernel.org/stable/c/9e9fa5ad37c9cbad73c165c7ff1e76e650825e7c
      Referenceadded
      —
      https://git.kernel.org/stable/c/fdb24a820a5832ec4532273282cbd4f22c291a0d
      Referenceremoved
      https://git.kernel.org/stable/c/01ee0bcc29864b78249308e8b35042b09bbf5fe3
      —
      Referenceremoved
      https://git.kernel.org/stable/c/0c8ab092aec3ac4294940054772d30b511b16713
      —
      Referenceremoved
      https://git.kernel.org/stable/c/3b9499e7d677dd4366239a292238489a804936b2
      —
      Referenceremoved
      https://git.kernel.org/stable/c/3f68a9457a6190814377577374da75f872e0a013
      —
      Referenceremoved
      https://git.kernel.org/stable/c/60f679f643f3f36a8571ea585e4ce5d93ef952b5
      —
      Referenceremoved
      https://git.kernel.org/stable/c/6b847d65f5b0065e02080c61fad93d57d6686383
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9e9fa5ad37c9cbad73c165c7ff1e76e650825e7c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/fdb24a820a5832ec4532273282cbd4f22c291a0d
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/01ee0bcc29864b78249308e8b35042b09bbf5fe3 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/0c8ab092aec3ac4294940054772d30b511b16713 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/3b9499e7d677dd4366239a292238489a804936b2 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/3f68a9457a6190814377577374da75f872e0a013 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/60f679f643f3f36a8571ea585e4ce5d93ef952b5 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/6b847d65f5b0065e02080c61fad93d57d6686383 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/9e9fa5ad37c9cbad73c165c7ff1e76e650825e7c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/fdb24a820a5832ec4532273282cbd4f22c291a0d Types: Patch
      —

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

    2. Record modifiedSiemens ADP

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/23xxx/CVE-2026-23388.json">CVE-2026-23388</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

      Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

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