CVE-2021-3320Network attack vector

Device crash via mishandled IEEE 802.15.4 ACK frames

Published May 24, 2021 · Updated Sep 16, 2024

Type confusion in Zephyr RTOS 2.4.0 allows remote attackers to crash an IEEE 802.15.4 device with a crafted ACK frame. The IEEE 802.15.4 validator accepts ACK frames, but the L2 processing path does not handle that frame type and reaches a NULL pointer dereference. No authentication or user interaction is required; receipt of the malformed wireless frame crashes the affected device.

CVSS severity5.9
Medium
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Type confusion in Zephyr RTOS 2.4.0 allows remote attackers to crash an IEEE 802.15.4 device with a crafted ACK frame. The IEEE 802.15.4 validator accepts ACK frames, but the L2 processing path does not handle that frame type and reaches a NULL pointer dereference. No authentication or user interaction is required; receipt of the malformed wireless frame crashes the affected device.

The record

CVE
CVE-2021-3320
Published
May 24, 2021
Updated
Sep 16, 2024
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-843, CWE-476, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=v2.4.0 <unspecified

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=v2.4.0 <unspecified

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.9Zephyr ProjectCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-843Access of Resource Using Incompatible Type ('Type Confusion')
CWE-476NULL Pointer Dereference
T1499Endpoint Denial of Service

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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