CVE-2021-34148: The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 devices does n

Q: How do I fix CVE-2021-34148?

wireless internet connectivity for embedded devices: upgrade to newer than 2.9.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-34148 being exploited?

CVE-2021-34148 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-34148 affect?

CVE-2021-34148 affects wireless internet connectivity for embedded devices. Severity is medium (CVSS 6.5). 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 a greater ACL Length after completion of the LMP setup procedure, allowing a

Q: How urgent is CVE-2021-34148?

Priority 35/100. No elevated risk signals yet.

Routine

MEDIUM 6.5UPGRADE

CVE-2021-34148 is a medium-severity flaw (CVSS 6.5) affecting wireless internet connectivity for embedded devices. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 a greater ACL Length 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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Adjacent network
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 52%)
CISA exploited list	No
Published	2021-09-07
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: cypress

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-09-07 07:15 UTCPublished CVE record published
2026-06-17 03:55 UTCUpdated Record last modified

cypress wireless internet connectivity for embedded devices UPGRADE

Affected: <= 2.9.0

Fixed in: newer than 2.9.0

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-34148?

wireless internet connectivity for embedded devices: upgrade to newer than 2.9.0. Exact commands for each OS are on this page.

Is CVE-2021-34148 being exploited?

CVE-2021-34148 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-34148 affect?

CVE-2021-34148 affects wireless internet connectivity for embedded devices. Severity is medium (CVSS 6.5). 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 a greater ACL Length after completion of the LMP setup procedure, allowing a

How urgent is CVE-2021-34148?

Priority 35/100. No elevated risk signals yet.

Software pages

Bluetooth vulnerabilities

Related CVEs

CVE-2021-34147 MEDIUM 6.5 UPGRADE The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not prope
CVE-2021-34145 MEDIUM 5.3 UPGRADE The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 devices does n

References

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