HighCVE-2026-23395

    Linux Kernel: security vulnerability (CVE-2026-23395)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix accepting multiple L2CAP_ECRED_CONN_REQ Currently the code attempts to accept requests regardless of the command identifier which may cause multiple requests to be marked as pending (FLAG_DEFER_SETUP) which can cause more than L2CAP_ECRED_MAX_CID(5) to be allocated in l2cap_ecred_rsp_defer causing an overflow. The spec is quite clear that the same identifier shall not be used on subsequent requests: 'Within each signaling channel a different Identifier shall be used for each successive request or indication.' https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-62/out/en/host/logical-link-control-and-adaptation-protocol-specification.html#UUID-32a25a06-4aa4-c6c7-77c5-dcfe3682355d So this attempts to check if there are any channels pending with the same identifier and rejects if any are found.

    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 5.7..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..6.12.78
    • Linux Kernel lt 6.13..6.18.20
    • Linux Kernel lt 6.19..6.19.10
    • 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 6.12.78
    • Linux Kernel 6.18.20
    • Linux Kernel 6.19.10
    • Linux Kernel 7.0

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.8

    Priority

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

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

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

    0.3 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 19.7

    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
    62.61 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
    8.8 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
    8.8
    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
    0.3 %
    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
    19.7
    Elevated — this CVE ranks above at least 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
    CISA assessment (SSVC)
    Exploitation: none known · not 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-20

    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: Bluetooth: L2CAP: Fix accepting multiple L2CAP_ECRED_CONN_REQ Currently the code attempts to accept requests regardless of the command identifier which may cause multiple requests to be marked as pending (FLAG_DEFER_SETUP) which can cause more than L2CAP_ECRED_MAX_CID(5) to be allocated in l2cap_ecred_rsp_defer causing an overflow. The spec is quite clear that the same identifier shall not be used on subsequent requests: 'Within each signaling channel a different Identifier shall be used for each successive request or indication.' https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-62/out/en/host/logical-link-control-and-adaptation-protocol-specification.html#UUID-32a25a06-4aa4-c6c7-77c5-dcfe3682355d So this attempts to check if there are any channels pending with the same identifier and rejects if any are found.

    Source: Debian LTS Advisories, Debian Security Advisories, siemens_advisory, suse_csaf, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, ENISA EUVD, cvelistv5, NVD (NIST), Microsoft Security Update Guide, 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
    • 6.2 – < 6.6.130
    • 6.7 – < 6.12.78
    • 6.19 – < 6.19.10
    • 6.13 – < 6.18.20
    • 5.11 – < 5.15.203
    • 6.20 – < 7.0
    • 5.7 – < 5.10.253
    • 5.16 – < 6.1.167
    • 6.6.130
    • 6.12.78
    • 6.19.10
    • 6.18.20
    • 5.15.203
    • 7.0
    • 5.10.253
    • 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_kernel5.7
    Linuxlinuxlinux_kernel7.0
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-20Improper Input Validation

      Class

      The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

      Entry at MITRE CWE-20

    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 modifiedCISA ADP

      Weakness type: CWE-20

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-20

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

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-23395","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:07:40.817542Z"}

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

    3. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/10a7a702542240d5edb2b39450ac951c59ccd009
      Referenceadded
      —
      https://git.kernel.org/stable/c/2124d82fd25e1671bb3ceb37998af5aae5903e06
      Referenceadded
      —
      https://git.kernel.org/stable/c/46e5b71666fb7652082e4e214a3365f4b14f1dc3
      Referenceadded
      —
      https://git.kernel.org/stable/c/5b3e2052334f2ff6d5200e952f4aa66994d09899
      Referenceadded
      —
      https://git.kernel.org/stable/c/6b949a6b33cbdf621d9fc6f0c48ac00915dbf514
      Referenceadded
      —
      https://git.kernel.org/stable/c/8d0d94f8ba5b3a0beec3b0da558b9bea48018117
      Referenceadded
      —
      https://git.kernel.org/stable/c/e72ee455297b794b852e5cea8d2d7bb17312172a
      Referenceadded
      —
      https://git.kernel.org/stable/c/fb4a3a26483f3ea2cd21c7a2f7c45d5670600465
      Referenceremoved
      https://git.kernel.org/stable/c/10a7a702542240d5edb2b39450ac951c59ccd009
      —
      Referenceremoved
      https://git.kernel.org/stable/c/2124d82fd25e1671bb3ceb37998af5aae5903e06
      —
      Referenceremoved
      https://git.kernel.org/stable/c/46e5b71666fb7652082e4e214a3365f4b14f1dc3
      —
      Referenceremoved
      https://git.kernel.org/stable/c/5b3e2052334f2ff6d5200e952f4aa66994d09899
      —
      Referenceremoved
      https://git.kernel.org/stable/c/6b949a6b33cbdf621d9fc6f0c48ac00915dbf514
      —
      Referenceremoved
      https://git.kernel.org/stable/c/8d0d94f8ba5b3a0beec3b0da558b9bea48018117
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e72ee455297b794b852e5cea8d2d7bb17312172a
      —
      Referenceremoved
      https://git.kernel.org/stable/c/fb4a3a26483f3ea2cd21c7a2f7c45d5670600465
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/10a7a702542240d5edb2b39450ac951c59ccd009 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/2124d82fd25e1671bb3ceb37998af5aae5903e06 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/46e5b71666fb7652082e4e214a3365f4b14f1dc3 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/5b3e2052334f2ff6d5200e952f4aa66994d09899 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/6b949a6b33cbdf621d9fc6f0c48ac00915dbf514 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8d0d94f8ba5b3a0beec3b0da558b9bea48018117 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e72ee455297b794b852e5cea8d2d7bb17312172a Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/fb4a3a26483f3ea2cd21c7a2f7c45d5670600465 Types: Patch
      —

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

    4. 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-2026-23395.json">CVE-2026-23395</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

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