What is CVE-2021-3320?

CVE-2021-3320 is a medium-severity vulnerability in Zephyrproject Zephyr, classified under NULL Pointer Dereference. CVSS score: 5.9/10. Published 2021-05-25.

How severe is CVE-2021-3320?

Medium severity. CVSS v3 base score is 5.9 out of 10.

NULL pointer dereference in Zephyrproject Zephyr

CVE-2021-3320

Type Confusion in 802154 ACK Frames Handling. Zephyr versions >= v2.4.0 contain NULL Pointer Dereference (CWE-476). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-27r3-rxch-2hm7

Published 2021-05-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.008 (56.4th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 56.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Zephyrproject Zephyr
Zephyrproject-Rtos Zephyr — versions v2.4.0

Weakness classification (CWE)

References

github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-27r3-rxch-2hm7 (Third Party Advisory)

Frequently asked questions

What is CVE-2021-3320?: CVE-2021-3320 is a medium-severity vulnerability in Zephyrproject Zephyr, classified under NULL Pointer Dereference. CVSS score: 5.9/10. Published 2021-05-25.
How severe is CVE-2021-3320?: Medium severity. CVSS v3 base score is 5.9 out of 10.