MediumCVE-2026-23356

    Linux Kernel: security vulnerability (CVE-2026-23356)

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

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    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: drbd: fix "LOGIC BUG" in drbd_al_begin_io_nonblock() Even though we check that we "should" be able to do lc_get_cumulative() while holding the device->al_lock spinlock, it may still fail, if some other code path decided to do lc_try_lock() with bad timing. If that happened, we logged "LOGIC BUG for enr=...", but still did not return an error.

    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 3.10..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

    6.3

    Priority

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

    Source: Vendor (CNA), CVSS v3

    5.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 3.0

    Show all metrics
    Severity
    Medium
    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
    42.93 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
    6.3 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
    5.5
    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
    3.0
    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
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    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: drbd: fix "LOGIC BUG" in drbd_al_begin_io_nonblock() Even though we check that we "should" be able to do lc_get_cumulative() while holding the device->al_lock spinlock, it may still fail, if some other code path decided to do lc_try_lock() with bad timing. If that happened, we logged "LOGIC BUG for enr=...", but still did not return an error. The rest of the code now assumed that this request has references for the relevant activity log extents. The implcations are that during an active resync, mutual exclusivity of resync versus application IO is not guaranteed. And a potential crash at this point may not realizs that these extents could have been target of in-flight IO and would need to be resynced just in case. Also, once the request completes, it will give up activity log references it does not even hold, which will trigger a BUG_ON(refcnt == 0) in lc_put(). Fix: Do not crash the kernel for a condition that is harmless during normal operation: also catch "e->refcnt == 0", not only "e == NULL" when being noisy about "al_complete_io() called on inactive extent %u\n". And do not try to be smart and "guess" whether something will work, then be surprised when it does not. Deal with the fact that it may or may not work. If it does not, remember a possible "partially in activity log" state (only possible for requests that cross extent boundaries), and return an error code from drbd_al_begin_io_nonblock(). A latter call for the same request will then resume from where we left off.

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

    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
    • 3.10 – < 5.10.253
    • 6.2 – < 6.6.130
    • 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
    • 5.10.253
    • 6.6.130
    • 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_kernel3.10
    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 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-2026-23356.json">CVE-2026-23356</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

    2. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/7752569fc78e89794ce28946529850282233f99d
      Referenceadded
      —
      https://git.kernel.org/stable/c/933d161baa3794547adee621c0bf52cbf2c1b3cd
      Referenceadded
      —
      https://git.kernel.org/stable/c/ab140365fb62c0bdab22b2f516aff563b2559e3b
      Referenceadded
      —
      https://git.kernel.org/stable/c/cf01aa6288e1190f89865e765056e2a9d8190639
      Referenceadded
      —
      https://git.kernel.org/stable/c/d1ef3aed4df2ef1fe46befd8f2da9a6ec5445508
      Referenceadded
      —
      https://git.kernel.org/stable/c/e91d8d6565b7819d13dab21d4dbed5b45efba59b
      Referenceadded
      —
      https://git.kernel.org/stable/c/eef1390125b660b8b61f9f227a03bb9c5e6d36a5
      Referenceadded
      —
      https://git.kernel.org/stable/c/f558e5404a72054b525dced1a0c66aa95a144153
      Referenceremoved
      https://git.kernel.org/stable/c/7752569fc78e89794ce28946529850282233f99d
      —
      Referenceremoved
      https://git.kernel.org/stable/c/933d161baa3794547adee621c0bf52cbf2c1b3cd
      —
      Referenceremoved
      https://git.kernel.org/stable/c/ab140365fb62c0bdab22b2f516aff563b2559e3b
      —
      Referenceremoved
      https://git.kernel.org/stable/c/cf01aa6288e1190f89865e765056e2a9d8190639
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d1ef3aed4df2ef1fe46befd8f2da9a6ec5445508
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e91d8d6565b7819d13dab21d4dbed5b45efba59b
      —
      Referenceremoved
      https://git.kernel.org/stable/c/eef1390125b660b8b61f9f227a03bb9c5e6d36a5
      —
      Referenceremoved
      https://git.kernel.org/stable/c/f558e5404a72054b525dced1a0c66aa95a144153
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/7752569fc78e89794ce28946529850282233f99d Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/933d161baa3794547adee621c0bf52cbf2c1b3cd Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/ab140365fb62c0bdab22b2f516aff563b2559e3b Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/cf01aa6288e1190f89865e765056e2a9d8190639 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d1ef3aed4df2ef1fe46befd8f2da9a6ec5445508 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e91d8d6565b7819d13dab21d4dbed5b45efba59b Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/eef1390125b660b8b61f9f227a03bb9c5e6d36a5 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/f558e5404a72054b525dced1a0c66aa95a144153 Types: Patch
      —

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

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