CVE-2021-3625

Memory corruption via unchecked DFU transfer length

Published Oct 5, 2021 · Updated Sep 16, 2024

Heap-based buffer overflow in Zephyr RTOS 2.5.0 allows physically proximate attackers to corrupt memory via a crafted USB DFU request. The dfu_class_handle_req function passes the request-controlled wLength to memcpy without limiting it to CONFIG_USB_REQUEST_BUFFER_SIZE, overrunning dfu_data_worker.buf. A target must expose the USB DFU class; a successful overwrite corrupts adjacent structures, and code-execution potential depends on build-specific memory layout.

CVSS severity9.6
Critical
EPSS probability2.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Zephyr RTOS 2.5.0 allows physically proximate attackers to corrupt memory via a crafted USB DFU request. The dfu_class_handle_req function passes the request-controlled wLength to memcpy without limiting it to CONFIG_USB_REQUEST_BUFFER_SIZE, overrunning dfu_data_worker.buf. A target must expose the USB DFU class; a successful overwrite corrupts adjacent structures, and code-execution potential depends on build-specific memory layout.

The record

CVE
CVE-2021-3625
Published
Oct 5, 2021
Updated
Sep 16, 2024
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-122, T1200
Attack vector
physical
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?

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

  1. Affected versionversion=v2.5.0 <unspecified

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=v2.5.0 <unspecified

Published CVSS scores

9.6GitHub Security AdvisoryCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:H/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.

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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)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1200Hardware Additions

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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