CVE-2021-42553

Arbitrary code execution via endpoint descriptor overflow

Published Oct 21, 2022 · Updated May 7, 2025

Buffer overflow in the STM32Cube USB Host Library before 3.5.1 allows attackers to execute arbitrary code via a crafted USB descriptor. The configuration-descriptor parser writes every declared endpoint into the fixed-size Ep_Desc array without enforcing USBH_MAX_NUM_ENDPOINTS, overwriting later USBH_HandleTypeDef members, including function pointers. Exploitation requires firmware containing the library to enumerate a maliciously formed USB peripheral; the resulting overwrite grants control of the embedded target.

CVSS severity6.8
Medium
EPSS probability1.05%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in the STM32Cube USB Host Library before 3.5.1 allows attackers to execute arbitrary code via a crafted USB descriptor. The configuration-descriptor parser writes every declared endpoint into the fixed-size Ep_Desc array without enforcing USBH_MAX_NUM_ENDPOINTS, overwriting later USBH_HandleTypeDef members, including function pointers. Exploitation requires firmware containing the library to enumerate a maliciously formed USB peripheral; the resulting overwrite grants control of the embedded target.

The record

CVE
CVE-2021-42553
Published
Oct 21, 2022
Updated
May 7, 2025
Vendor
STMicroelectronics
Product
STM32Cube USB Host Library
Classifications
CWE-120, T1200
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 21, 2022CVE publishedPublication date reported by the CVE source.
  2. May 7, 2025Record 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=all <3.5.1

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

STMicroelectronics · STM32Cube USB Host Libraryversion=all <3.5.1

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
6.8Switzerland Government Common Vulnerability ProgramCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/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-120Buffer Copy without Checking Size of Input ('Classic 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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