CVE-2021-32020Network attack vector

Code execution or crash via allocation-size overflow

Published May 3, 2021 · Updated Aug 3, 2024

Integer overflow in AWS FreeRTOS Kernel before 10.4.3 allows remote attackers to execute code or crash devices via oversized allocations. The pvPortMalloc implementations add allocator metadata and alignment padding to xWantedSize without first rejecting size_t wraparound, causing a large request to receive an undersized heap buffer. Exploitation requires application code to derive the allocation size from attacker-controlled input; the device and heap implementation determine the resulting code execution or crash.

CVSS severity9.8
Critical
EPSS probability1.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in AWS FreeRTOS Kernel before 10.4.3 allows remote attackers to execute code or crash devices via oversized allocations. The pvPortMalloc implementations add allocator metadata and alignment padding to xWantedSize without first rejecting size_t wraparound, causing a large request to receive an undersized heap buffer. Exploitation requires application code to derive the allocation size from attacker-controlled input; the device and heap implementation determine the resulting code execution or crash.

The record

CVE
CVE-2021-32020
Published
May 3, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-119, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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