What is CVE-2021-32020?

CVE-2021-32020 is a critical-severity vulnerability in Amazon Freertos, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2021-05-03.

How severe is CVE-2021-32020?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Amazon Freertos

CVE-2021-32020

The kernel in Amazon Web Services FreeRTOS before 10.4.3 has insufficient bounds checking during management of heap memory.

Vulnerability class: Buffer Overflow

Published 2021-05-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.013 (69.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 69th percentile — 69.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: 0.000

Affected products

Amazon Freertos

Weakness classification (CWE)

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

References

github.com/FreeRTOS/FreeRTOS-Kernel/commit/c7a9a01c94987082b223d3e59969ede64363… (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-32020?: CVE-2021-32020 is a critical-severity vulnerability in Amazon Freertos, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2021-05-03.
How severe is CVE-2021-32020?: Critical severity. CVSS v3 base score is 9.8 out of 10.