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CVE-2026-53208 Linux CVE debrief

CVE-2026-53208 is a vulnerability in the Linux kernel's Bluetooth L2CAP protocol. The vulnerability allows a Bluetooth BR/EDR peer within radio range to force 168 ECHO_RSP frames from one 681-byte fixed-channel signaling packet containing packed ECHO_REQ commands. This issue was resolved by defining Linux's BR/EDR signaling MTU as the spec minimum of 48 bytes and rejecting any larger signaling packet with one L2CAP_COMMAND_REJECT_RSP carrying L2CAP_REJ_MTU_EXCEEDED before any command is dispatched. 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.

Vendor
Linux
Product
Unknown
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-25
Original CVE updated
2026-07-02
Advisory published
2026-06-25
Advisory updated
2026-07-02

Who should care

Organizations using Linux kernel-based systems with Bluetooth capabilities should be aware of this vulnerability. They should prioritize patching and monitoring their systems for potential exploitation. The vulnerability's impact is limited to Bluetooth BR/EDR peers within radio range, before pairing.

Technical summary

The Linux kernel's Bluetooth L2CAP protocol has a vulnerability (CVE-2026-53208) that allows a Bluetooth BR/EDR peer within radio range to send a fixed-channel CID 0x0001 packet larger than MTUsig, containing many L2CAP_ECHO_REQ commands before pairing. The target transmits 168 ECHO_RSP frames over about 220 ms in response to one 681-byte signaling packet with 168 zero-length ECHO_REQ commands. To address this, Linux's BR/EDR signaling MTU is defined as 48 bytes, and larger signaling packets are rejected with L2CAP_COMMAND_REJECT_RSP and L2CAP_REJ_MTU_EXCEEDED.

Defensive priority

Apply patches to Linux kernel systems with Bluetooth capabilities to prevent exploitation. Monitor system logs for suspicious Bluetooth activity.

Recommended defensive actions

  • Apply patches to Linux kernel systems with Bluetooth capabilities
  • Monitor system logs for suspicious Bluetooth activity
  • Verify Bluetooth device configurations and restrict access if necessary
  • Implement network segmentation to limit the spread of potential exploitation
  • Conduct regular vulnerability assessments and penetration testing

Evidence notes

The CVE-2026-53208 vulnerability was introduced in the initial git import of the Linux kernel. The vulnerability allows a Bluetooth BR/EDR peer within radio range to force 168 ECHO_RSP frames from one 681-byte fixed-channel signaling packet containing packed ECHO_REQ commands. The issue was resolved by defining Linux's BR/EDR signaling MTU as 48 bytes and rejecting larger signaling packets.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-53208 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-53208

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-53208 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-53208

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/214a2042b16b3c8d798a8b9ef9f36094f13a9859

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/a8335f3db15bd1e0e82e0db5d488fabc7d10d1ab

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/b20e8a98dd29b121f58fcdf51e8576119aba536a

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/dd214733544427587a95f66dbf3adff072568990

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/dedc92b96dc1d8919a3bdf2495ede68922ef7ebc

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/e05c4ac575b457978a7ef441053394169084869c

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/e2b8acf9405bd9b1baf1c54dc897b0905db689bf

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.