HighCVE-2026-53208

    Linux Kernel: security vulnerability (CVE-2026-53208)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: reject BR/EDR signaling packets over MTUsig net/bluetooth/l2cap_core.c:l2cap_sig_channel() accepts BR/EDR signaling packets up to the channel MTU and dispatches each command without enforcing the signaling MTU (MTUsig). A Bluetooth BR/EDR peer within radio range can send a fixed-channel CID 0x0001 packet that is larger than MTUsig and contains many L2CAP_ECHO_REQ commands before pairing.

    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 2.6.12..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..6.12.94
    • Linux Kernel lt 6.13..6.18.36
    • Linux Kernel lt 6.19..7.0.13
    Fixed in
    • Linux Kernel 5.10.259
    • Linux Kernel 5.15.210
    • Linux Kernel 6.1.176
    • Linux Kernel 6.6.143
    • Linux Kernel 6.12.94
    • Linux Kernel 6.18.36
    • Linux Kernel 7.0.13
    • Linux Kernel 7.1

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

    Metrics

    7.0

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

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.2

    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
    47.01 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
    7.0 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
    2.2
    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: Bluetooth: L2CAP: reject BR/EDR signaling packets over MTUsig net/bluetooth/l2cap_core.c:l2cap_sig_channel() accepts BR/EDR signaling packets up to the channel MTU and dispatches each command without enforcing the signaling MTU (MTUsig). A Bluetooth BR/EDR peer within radio range can send a fixed-channel CID 0x0001 packet that is larger than MTUsig and contains many L2CAP_ECHO_REQ commands before pairing. In a real-radio stock-kernel run, one 681-byte signaling packet containing 168 zero-length ECHO_REQ commands made the target transmit 168 ECHO_RSP frames over about 220 ms. Impact: a Bluetooth BR/EDR peer within radio range, before pairing, can force 168 ECHO_RSP frames from one 681-byte fixed-channel signaling packet containing packed ECHO_REQ commands. Define Linux's BR/EDR signaling MTU as the spec minimum of 48 bytes and reject any larger signaling packet with one L2CAP_COMMAND_REJECT_RSP carrying L2CAP_REJ_MTU_EXCEEDED before any command is dispatched. The Bluetooth Core spec wording for MTUExceeded says the reject identifier shall match the first request command in the packet, and that packets containing only responses shall be silently discarded. Linux intentionally deviates from that prescription: silently discarding desynchronizes the peer because the remote stack never learns its responses were dropped, and locating the first request command requires walking command headers past MTUsig, i.e. processing bytes from a packet we have already decided is too large to process. We therefore always emit one reject and use the identifier from the first command header, a single fixed-offset byte read. The unrestricted BR/EDR signaling parser and ECHO_REQ response path both trace to the initial git import; no later introducing commit is available for a Fixes tag.

    Source: suse_csaf, Debian LTS Advisories, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, siemens_advisory, 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
    • 2.6.12 – < 5.10.259
    • 6.7 – < 6.12.94
    • 6.13 – < 6.18.36
    • 5.11 – < 5.15.210
    • —
    • 5.16 – < 6.1.176
    • 6.19 – < 7.0.13
    • 6.2 – < 6.6.143
    • 5.10.259
    • 6.12.94
    • 6.18.36
    • 5.15.210
    • 7.1
    • 6.1.176
    • 7.0.13
    • 6.6.143
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinux-6.1bullseye
    Linuxubuntulinux-oracle-7.0noble
    Linuxlinuxlinux_kernel2.6.12
    Linuxlinuxlinux_kernel7.1
    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/214a2042b16b3c8d798a8b9ef9f36094f13a9859
      Referenceadded
      —
      https://git.kernel.org/stable/c/a8335f3db15bd1e0e82e0db5d488fabc7d10d1ab
      Referenceadded
      —
      https://git.kernel.org/stable/c/b20e8a98dd29b121f58fcdf51e8576119aba536a
      Referenceadded
      —
      https://git.kernel.org/stable/c/dd214733544427587a95f66dbf3adff072568990
      Referenceadded
      —
      https://git.kernel.org/stable/c/dedc92b96dc1d8919a3bdf2495ede68922ef7ebc
      Referenceadded
      —
      https://git.kernel.org/stable/c/e05c4ac575b457978a7ef441053394169084869c
      Referenceadded
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      https://git.kernel.org/stable/c/e2b8acf9405bd9b1baf1c54dc897b0905db689bf
      Referenceadded
      —
      https://git.kernel.org/stable/c/fa5823126239b3e453fac1a2fe50726c7f4a55e1
      Referenceremoved
      https://git.kernel.org/stable/c/214a2042b16b3c8d798a8b9ef9f36094f13a9859
      —
      Referenceremoved
      https://git.kernel.org/stable/c/a8335f3db15bd1e0e82e0db5d488fabc7d10d1ab
      —
      Referenceremoved
      https://git.kernel.org/stable/c/b20e8a98dd29b121f58fcdf51e8576119aba536a
      —
      Referenceremoved
      https://git.kernel.org/stable/c/dd214733544427587a95f66dbf3adff072568990
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      Referenceremoved
      https://git.kernel.org/stable/c/dedc92b96dc1d8919a3bdf2495ede68922ef7ebc
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      Referenceremoved
      https://git.kernel.org/stable/c/e05c4ac575b457978a7ef441053394169084869c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e2b8acf9405bd9b1baf1c54dc897b0905db689bf
      —
      Referenceremoved
      https://git.kernel.org/stable/c/fa5823126239b3e453fac1a2fe50726c7f4a55e1
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/214a2042b16b3c8d798a8b9ef9f36094f13a9859 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/a8335f3db15bd1e0e82e0db5d488fabc7d10d1ab Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/b20e8a98dd29b121f58fcdf51e8576119aba536a Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/dd214733544427587a95f66dbf3adff072568990 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/dedc92b96dc1d8919a3bdf2495ede68922ef7ebc Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e05c4ac575b457978a7ef441053394169084869c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e2b8acf9405bd9b1baf1c54dc897b0905db689bf Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/fa5823126239b3e453fac1a2fe50726c7f4a55e1 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/2026/53xxx/CVE-2026-53208.json">CVE-2026-53208</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

    3. Initial analysis by NVDNVD

      Newly listed as affected:
      • Linux Kernel (5.16 – before 6.1.176; 6.2 – before 6.6.143; 5.11 – before 5.15.210; 6.13 – before 6.18.36; 6.7 – before 6.12.94; 6.19 – before 7.0.13; 2.6.12.1 – before 5.10.259; 11 individual versions)

      CVSS V3.1: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

      Show 11 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
      Weakness type (CWE)added
      —
      NVD-CWE-noinfo
      Product configurationadded
      —
      OR *cpe:2.3:o:linux:linux_kernel:2.6.12:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:2.6.12:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:2.6.12:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:2.6.12:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:2.6.12:-:*:*:*:*:*:* *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) 6.2 up to (excluding) 6.6.143 *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:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.18.36 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.12.94 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.13 *cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc6:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 2.6.12.1 up to (excluding) 5.10.259
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/214a2042b16b3c8d798a8b9ef9f36094f13a9859 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/a8335f3db15bd1e0e82e0db5d488fabc7d10d1ab Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/b20e8a98dd29b121f58fcdf51e8576119aba536a Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/dd214733544427587a95f66dbf3adff072568990 Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/dedc92b96dc1d8919a3bdf2495ede68922ef7ebc Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/e05c4ac575b457978a7ef441053394169084869c Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/e2b8acf9405bd9b1baf1c54dc897b0905db689bf Types: Patch
      Reference typeadded
      —
      kernel.org: https://git.kernel.org/stable/c/fa5823126239b3e453fac1a2fe50726c7f4a55e1 Types: Patch

      Source identifier: nvd@nist.gov

    4. Record modifiedLinux

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      Linux, Linux
      Linux, Linux

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

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