CVE-2021-3835

Memory corruption via unchecked USB transfer length

Published Feb 7, 2022 · Updated Sep 17, 2024

Heap-based buffer overflow in Zephyr RTOS from 2.6.0 allows physically proximate attackers to corrupt memory via a crafted USB control transfer. The Bluetooth USB class handler passes the request length to bt_buf_get_tx, which copies request data into a fixed-size HCI command buffer without checking available tailroom. A device must expose the Bluetooth USB device class; the overwrite reaches adjacent heap data and enables data-structure corruption or arbitrary code execution.

CVSS severity8.2
High
EPSS probability0.74%
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 from 2.6.0 allows physically proximate attackers to corrupt memory via a crafted USB control transfer. The Bluetooth USB class handler passes the request length to bt_buf_get_tx, which copies request data into a fixed-size HCI command buffer without checking available tailroom. A device must expose the Bluetooth USB device class; the overwrite reaches adjacent heap data and enables data-structure corruption or arbitrary code execution.

The record

CVE
CVE-2021-3835
Published
Feb 7, 2022
Updated
Sep 17, 2024
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-122, CWE-787
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 7, 2022CVE 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=v2.6.0 <unspecified

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=v2.6.0 <unspecified

Published CVSS scores

5.8NIST NVDAV:A/AC:L/Au:N/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.2Zephyr ProjectCVSS:3.1/AV:A/AC:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
CWE-787Out-of-bounds Write

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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