CVE-2021-3455: Disconnecting L2CAP channel right after invalid ATT request leads freeze

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-10-19 · updated 2026-06-17
Weakness: CWE-416

Description

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

Affected products

zephyrproject zephyr: from 2.4.0 before 2.6.0 — fixed in 2.6.0

How to fix

Upgrade to a fixed version: zephyrproject zephyr 2.6.0. Check the vendor advisory for mitigations.

References

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

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