CVE-2021-34147
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1...
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.
Attack profile
How easy it is to exploit
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
6.5
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.
- Record
CVE-2021-34147- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 6.1 Medium
AV:A/AC:L/Au:N/C:N/I:N/A:C - Updated
- 2026-11-02
CVE List No score
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.
- Record
CVE-2021-34147- Updated
- 2026-11-02
EUVDEUVD-2021-20809 No score
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.
- Record
EUVD-2021-20809- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-m739-9w4c-mx4g No score
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1...
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.
- Record
GHSA-m739-9w4c-mx4g- Updated
- 2026-11-02
OSV
6.5
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.
- Record
CVE-2021-34147- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-34147
6.5
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.
- Record
DEBIAN-CVE-2021-34147- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-34147
6.5
The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.
- Record
UBUNTU-CVE-2021-34147- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
bluez-firmwareDebian:12 |
before 1.2-8, plus listed versions 1.0-21.0-31.2-11.2-21.2-3 Show 6 moreShow less1.2-41.2-51.2-61.2-71.2-7~bpo11+11.2-8~bpo11+1 |
1.2-8 |
bluez-firmwareDebian:13 |
before 1.2-8, plus listed versions 1.0-21.0-31.2-11.2-21.2-3 Show 6 moreShow less1.2-41.2-51.2-61.2-71.2-7~bpo11+11.2-8~bpo11+1 |
1.2-8 |
bluez-firmwareDebian:14 |
before 1.2-8, plus listed versions 1.0-21.0-31.2-11.2-21.2-3 Show 6 moreShow less1.2-41.2-51.2-61.2-71.2-7~bpo11+11.2-8~bpo11+1 |
1.2-8 |
bluez-firmwareUbuntu:22.04:LTS |
All versions, plus listed versions 1.2-7 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-34147 is a medium vulnerability (CVSS 6.5) in Cypress Wireless Internet Connectivity For Embedded Devices, published September 7, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.59%, the 48th percentile. Fixed in bluez-firmware 1.2-8.
References
cypress.com/documentation/datasheets/cyw20735b1-single-chip-bluetooth-transceiver-wireless-input-devices
dl.packetstormsecurity.net/papers/general/braktooth.pdf
nvd.nist.gov/vuln/detail/CVE-2021-34147
github.com/advisories/GHSA-m739-9w4c-mx4g
security-tracker.debian.org/tracker/CVE-2021-34147
ubuntu.com/security/CVE-2021-34147
github.com/RPi-Distro/bluez-firmware/commit/31ad68831357d2019624004f1f0846475671088f
cve.org/CVERecord?id=CVE-2021-34147