CVE-2021-34148Public exploit

Firmware crash via oversized LMP_max_slot packet

Published Sep 7, 2021 · Updated Aug 4, 2024

Denial of service in Cypress WICED BT stack 2.9.0 and earlier allows physically proximate attackers to crash CYW20735B1 firmware. After LMP setup completes, the Bluetooth Classic baseband accepts an LMP_max_slot packet declaring ACL Length 31 instead of rejecting the oversized value. No pairing or authentication is required, but exploitation requires Bluetooth radio proximity and intentionally crashes the target device's firmware.

CVSS severity6.5
Medium
EPSS probability0.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cypress WICED BT stack 2.9.0 and earlier allows physically proximate attackers to crash CYW20735B1 firmware. After LMP setup completes, the Bluetooth Classic baseband accepts an LMP_max_slot packet declaring ACL Length 31 instead of rejecting the oversized value. No pairing or authentication is required, but exploitation requires Bluetooth radio proximity and intentionally crashes the target device's firmware.

The record

CVE
CVE-2021-34148
Published
Sep 7, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:C
6.5NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1499.004Application or System Exploitation Flood

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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