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Wireless Internet Connectivity For Embedded DevicesOperating system · Cypress

CVE-2021-34145

MEDIUM · 5.3 CVSS v3.1 Published 2021-09-07
Fix available
A fix is available. Upgrade to after 2.9.0 or later.
See remediation →
58/100
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 WICED BT stack through 2.9.0 for CYW20735B1 devices does not properly handle the reception of LMP_max_slot with an invalid Baseband packet type (and LT_ADDRESS and LT_ADDR) after completion of the LMP setup procedure, allowing attackers in radio range to trigger a denial of service (firmware crash) via a crafted LMP packet.

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 · moderate confidence

The Cypress WICED BT stack for CYW20735B1 devices fails to properly validate LMP_max_slot messages containing invalid Baseband packet types (with invalid LT_ADDRESS and LT_ADDR fields) after the LMP setup procedure completes. This allows nearby attackers to send crafted LMP packets that cause a firmware crash and denial of service.

MitigationContact Cypress/Infineon for the patched firmware version. If no patch is available, minimize exposure by restricting physical proximity to trusted Bluetooth environments, as exploitation requires the attacker to be within radio range.

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
Wireless Internet Connectivity For Embedded DevicesOperating system
Affected:<= 2.9.0

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/AC:H/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 Bluetooth chipset
    Check device documentation, BOM (bill of materials), or use Bluetooth host tooling (e.g., hcitool, btmgmt) to query the controller for chipset identification. Look for Cypress CYW20735B1 or Broadcom/Infineon Bluetooth silicon.
    Affected if The device uses a CYW20735B1 chipset
  2. Check the WICED BT stack version
    Consult device firmware release notes, system logs, or contact the device vendor/manufacturer to obtain the installed WICED BT stack version. This is typically embedded in the Bluetooth firmware and not easily readable via standard host tools.
    Affected if The WICED BT stack version is 2.9.0 or lower, or the version cannot be determined but the chipset is CYW20735B1
  3. Verify Bluetooth is enabled
    Check if Bluetooth is actively enabled on the device. On Linux, use 'rfkill list' or 'hciconfig' to see if the Bluetooth controller is powered up. On embedded systems, check system configuration or GPIO states.
    Affected if Bluetooth is powered on and in discoverable or connectable mode, as the attack requires radio proximity
  4. Assess physical exposure
    Evaluate whether the device operates in a controlled or trusted physical environment. Determine if untrusted individuals could gain radio proximity to the device.
    Affected if The device is in an environment where untrusted parties could be within Bluetooth radio range

A user is affected if the device contains a CYW20735B1 chipset running WICED BT stack version 2.9.0 or lower, with Bluetooth enabled in an exposed physical setting.

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.

dbcve · scoped
Upgrade available Upgrade to a release after 2.9.0
Interim mitigation

Contact Cypress/Infineon for the patched firmware version. If no patch is available, minimize exposure by restricting physical proximity to trusted Bluetooth environments, as exploitation requires the attacker to be within radio range.

Recommended fix Moderate confidence

Cypress WICED BT stack version > 2.9.0 (contact Infineon/Cypress for the exact fixed release version)

  1. 1. Identify the Cypress WICED BT SDK version currently deployed on affected CYW20735B1 devices
  2. 2. Obtain the latest Cypress WICED BT stack firmware release for CYW20735B1 from the official Cypress/Infineon website
  3. 3. Review the release notes for the new version to confirm inclusion of the CVE-2021-34134145 fix
  4. 4. Apply the updated firmware to all affected devices following the standard Cypress firmware upgrade procedure
  5. 5. Verify the firmware update was successful and the device is functioning normally
  6. 6. Confirm the vulnerability is remediated by testing with a tool that can send crafted LMP packets (if available in a safe test environment)
Caveat Review SDK release notes for any API changes or behavioral differences that may affect existing applications

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Wireless Internet Connectivity For Embedded Devices Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
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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-2021-34145 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data