What is CVE-2021-3625?

CVE-2021-3625 is a critical-severity vulnerability in Zephyrproject Zephyr, classified under Heap-based Buffer Overflow. CVSS score: 9.6/10. Published 2021-10-05.

How severe is CVE-2021-3625?

Critical severity. CVSS v3 base score is 9.6 out of 10.

Is CVE-2021-3625 known to be exploited?

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

Buffer overflow in Zephyrproject Zephyr

CVE-2021-3625

Buffer overflow in Zephyr USB DFU DNLOAD. Zephyr versions >= v2.5.0 contain Heap-based Buffer Overflow (CWE-122). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-c3gr-hgvr-f363

Vulnerability class: Buffer Overflow

Published 2021-10-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.6 (Critical). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:H.

EPSS exploit prediction

EPSS: 0.023 (83.1th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 83rd percentile — 83.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.023 · newest: 0.023 · change: 0.000

Affected products

Zephyrproject Zephyr
Zephyrproject-Rtos Zephyr — versions v2.5.0

Weakness classification (CWE)

Public proof-of-concept exploits

References

github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-c3gr-hgvr-f363 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3625?: CVE-2021-3625 is a critical-severity vulnerability in Zephyrproject Zephyr, classified under Heap-based Buffer Overflow. CVSS score: 9.6/10. Published 2021-10-05.
How severe is CVE-2021-3625?: Critical severity. CVSS v3 base score is 9.6 out of 10.
Is CVE-2021-3625 known to be exploited?: 9 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.