What is CVE-2021-34145?

CVE-2021-34145 is a medium-severity vulnerability in Cypress Cyw20735b1. CVSS score: 5.3/10. Published 2021-09-07.

How severe is CVE-2021-34145?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Is CVE-2021-34145 known to be exploited?

4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Cypress Cyw20735b1

CVE-2021-34145

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.

Published 2021-09-07 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.005 (41.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 41st percentile — 41.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Public proof-of-concept exploits

References

www.cypress.com/documentation/datasheets/cyw20735b1-single-chip-bluetooth-trans… (Vendor Advisory)
dl.packetstormsecurity.net/papers/general/braktooth.pdf (Broken Link)

Frequently asked questions

What is CVE-2021-34145?: CVE-2021-34145 is a medium-severity vulnerability in Cypress Cyw20735b1. CVSS score: 5.3/10. Published 2021-09-07.
How severe is CVE-2021-34145?: Medium severity. CVSS v3 base score is 5.3 out of 10.
Is CVE-2021-34145 known to be exploited?: 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.