CVE-2021-3431

Adjacent service interruption via repeated Bluetooth feature requests

Published Jun 28, 2022 · Updated Sep 16, 2024

Reachable assertion in the Zephyr RTOS Bluetooth controller 2.5.0 allows adjacent attackers to interrupt operation via repeated LL_FEATURE_REQ PDUs. The Link Layer accepts duplicate Feature Exchange requests without enforcing transaction-violation checks, allocates a response for each request, and depletes the control transmit-PDU pool until event processing stalls and asserts. Exploitation requires Bluetooth proximity and an established link in which the peer repeatedly sends new requests while rejecting controller responses; no data disclosure or modification is reported.

CVSS severity4.3
Medium
EPSS probability0.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in the Zephyr RTOS Bluetooth controller 2.5.0 allows adjacent attackers to interrupt operation via repeated LL_FEATURE_REQ PDUs. The Link Layer accepts duplicate Feature Exchange requests without enforcing transaction-violation checks, allocates a response for each request, and depletes the control transmit-PDU pool until event processing stalls and asserts. Exploitation requires Bluetooth proximity and an established link in which the peer repeatedly sends new requests while rejecting controller responses; no data disclosure or modification is reported.

The record

CVE
CVE-2021-3431
Published
Jun 28, 2022
Updated
Sep 16, 2024
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-617, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 28, 2022CVE 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 vectoradjacent
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=v2.5.0 <unspecified

Published CVSS scores

4.3Zephyr ProjectCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS: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.

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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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-617Reachable Assertion
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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