CVE-2021-34268

Denial of service via unchecked packet size

Published Jul 22, 2021 · Updated Aug 4, 2024

Denial of service in STMicroelectronics STM32Cube Middleware 1.8.0 and earlier allows attackers to disrupt USB hosts via malformed device packets. USBH_ParseDevDesc() accepts an invalid bMaxPacketSize from the USB device descriptor and uses it to construct the control pipe without validating USB-allowed values. A physically proximate attacker can present the malformed device, causing control transfers to fail and repeated re-enumeration that hangs host communication until the device is removed or the system is reset.

CVSS severity4.6
Medium
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in STMicroelectronics STM32Cube Middleware 1.8.0 and earlier allows attackers to disrupt USB hosts via malformed device packets. USBH_ParseDevDesc() accepts an invalid bMaxPacketSize from the USB device descriptor and uses it to construct the control pipe without validating USB-allowed values. A physically proximate attacker can present the malformed device, causing control transfers to fail and repeated re-enumeration that hangs host communication until the device is removed or the system is reset.

The record

CVE
CVE-2021-34268
Published
Jul 22, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

2.1NVDAV:L/AC:L/Au:N/C:N/I:N/A:P
4.6NVDCVSS:3.1/AV:P/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.

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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

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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