CVE-2021-3330

Code execution via forged fragment list sorting

Published Oct 12, 2021 · Updated Sep 17, 2024

Out-of-bounds write in Zephyr RTOS 2.4.0 through 2.4.x allows remote attackers to corrupt memory via forged fragment lists. The fragment-list sorting routine corrupts linked-list state and performs a large out-of-bounds write while processing attacker-supplied network fragments. Adjacent-network unauthenticated attackers can trigger the flaw, causing denial of service and potentially code execution on affected embedded devices.

CVSS severity8.8
High
EPSS probability0.61%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Zephyr RTOS 2.4.0 through 2.4.x allows remote attackers to corrupt memory via forged fragment lists. The fragment-list sorting routine corrupts linked-list state and performs a large out-of-bounds write while processing attacker-supplied network fragments. Adjacent-network unauthenticated attackers can trigger the flaw, causing denial of service and potentially code execution on affected embedded devices.

The record

CVE
CVE-2021-3330
Published
Oct 12, 2021
Updated
Sep 17, 2024
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-787, T1210
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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=>=2.4.0 <unspecified

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=>=2.4.0 <unspecified

Published CVSS scores

8.8NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.8NVDAV:A/AC:L/Au:N/C:P/I:P/A:P
7.1Zephyr ProjectCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

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.

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No observations available

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

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1210Exploitation of Remote Services

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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