CVE-2021-3455

Disconnecting L2CAP channel right after invalid ATT request leads freeze

4.3 Medium

Disconnecting L2CAP channel right after invalid ATT request leads freeze. Zephyr versions >= 2.4.0, >= 2.5.0 contain Use After Free (CWE-416). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-7g38-3x9v-v7vp

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: Low

Exploit likelihood

1.11%Up 0.7 points since Oct 20, 2021

What each source reports

CVE List Score used 4.3

Disconnecting L2CAP channel right after invalid ATT request leads freeze

Record: CVE-2021-3455
CVSS 3.1: 4.3 MediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness: CWE-416
Updated: 2026-11-02

EUVDEUVD-2021-26778 4.3

Record: EUVD-2021-26778
CVSS 3.1: 4.3 MediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Updated: 2026-11-03

NVD 4.3

Record: CVE-2021-3455
CVSS 3.1: 4.3 MediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0: 5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness: CWE-416
Updated: 2026-11-02

Affected products

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases, published	EUVD
Nov 2, 2026	first indexed	CVE List, NVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-3455 is a medium vulnerability (CVSS 4.3) in Zephyrproject Zephyr, published October 19, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.11%, the 66th percentile. No source names a fixed version.

References

github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-7g38-3x9v-v7vp