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Cyw920735q60evb 01 FirmwareOperating system · Cypress

CVE-2021-34146

MEDIUM · 6.5 CVSS v3.1 Published 2021-09-07
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The Bluetooth Classic implementation in the Cypress CYW920735Q60EVB does not properly handle the reception of continuous unsolicited LMP responses, allowing attackers in radio range to trigger a denial of service and restart (crash) of the device by flooding it with LMP_AU_Rand packets after the paging procedure.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Cypress CYW920735Q60EVB Bluetooth Classic implementation fails to properly handle continuous unsolicited LMP (Link Manager Protocol) responses. Attackers within radio range can flood the device with LMP_AU_Rand packets after the paging procedure, causing a denial of service and device restart/crash due to improper state management in the LMP response handling logic.

MitigationApply vendor-supplied firmware updates for the Cypress CYW920735Q60EVB that address proper LMP response state management and rate limiting. If no update is available, consider network isolation to limit exposure to unauthorized Bluetooth devices.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Cyw920735q60evb 01 FirmwareOperating system
Affected:all versions
Cyw20735b1 FirmwareOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Cypress chip model
    Inspect the hardware labeling, device datasheet, or FCC ID. Look for markings indicating 'CYW920735Q60EVB' or 'CYW20735B1' chip. Check the BOM (Bill of Materials) or hardware schematics if available.
    Affected if The device uses a CYW920735Q60EVB or CYW20735B1 chip with Bluetooth Classic capability.
  2. Verify Bluetooth Classic is active
    Check if the device has Bluetooth Classic (BR/EDR) enabled, not just BLE. This can be done via Bluetooth stack configuration, HCI logs, or device manager showing BR/EDR support.
    Affected if Bluetooth Classic (BR/EDR) is enabled and the device accepts incoming Classic Bluetooth connections.
  3. Confirm Bluetooth exposure
    Check if the device is discoverable, connectable, or page-scan enabled. Review Bluetooth stack configuration for accessibility settings. Determine if the device operates in an environment where unauthorized Bluetooth devices could be within radio range.
    Affected if The device is discoverable or connectable to unauthenticated Bluetooth peers.
  4. Review HCI logs for LMP traffic
    Enable Bluetooth HCI logging on the device or use a Bluetooth analyzer to capture traffic. Examine logs after device startup for LMP_AU_Rand packets or unusually high volumes of LMP responses.
    Affected if Abnormal or excessive LMP packet activity is observed, particularly unsolicited LMP_AU_Rand packets after paging.
  5. Check for unexplained restarts
    Monitor system logs, crash dumps, or watchdog timers for unexpected device restarts or crashes that coincide with Bluetooth activity. Review any 'watchdog timeout' or 'panic' logs.
    Affected if The device exhibits spontaneous restarts or crashes when Bluetooth is active and within range of other devices.

A user is affected if they have a CYW920735Q60EVB or CYW20735B1 device with Bluetooth Classic enabled and the device is exposed to potential radio-range attackers who could flood it with LMP packets.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor-supplied firmware updates for the Cypress CYW920735Q60EVB that address proper LMP response state management and rate limiting. If no update is available, consider network isolation to limit exposure to unauthorized Bluetooth devices.

Fix this in Cyw920735q60evb 01 Firmware Scoped from the published advisory
  • Consultation6.0 h
  • Implementation20.0 h
  • Testing12.0 h
  • Review / QA6.0 h
44.0 hours of engineering $7,680
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-34146 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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