CVE-2021-3510Network attack vector

Device crash via nested-array length overwrite

Published Oct 5, 2021 · Updated Sep 16, 2024

Improper nested-array decoding in Zephyr RTOS allows remote attackers to crash affected devices through crafted JSON input. The arr_parse routine treats a JSON_TOK_LIST_START descriptor union member as an object, uses its unrelated offset relative to the parent, and writes the subarray length over a parent field. The application must parse attacker-controlled nested arrays with JSON_OBJ_DESCR_ARRAY_ARRAY; the resulting parent-object corruption can terminate the device.

CVSS severity7.5
High
EPSS probability0.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper nested-array decoding in Zephyr RTOS allows remote attackers to crash affected devices through crafted JSON input. The arr_parse routine treats a JSON_TOK_LIST_START descriptor union member as an object, uses its unrelated offset relative to the parent, and writes the subarray length over a parent field. The application must parse attacker-controlled nested arrays with JSON_OBJ_DESCR_ARRAY_ARRAY; the resulting parent-object corruption can terminate the device.

The record

CVE
CVE-2021-3510
Published
Oct 5, 2021
Updated
Sep 16, 2024
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-588, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 5, 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?

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  1. Affected versionversion=>1.14.0 <unspecified
  2. Affected versionversion=>2.5.0 <unspecified

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=>1.14.0 <unspecified; version=>2.5.0 <unspecified

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5Zephyr ProjectCVSS:3.1/AV:N/AC:L/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 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-588Attempt to Access Child of a Non-structure Pointer
T1499.004Application or System Exploitation

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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