CVE-2021-3454

Service interruption via truncated L2CAP SDU length

Published Oct 19, 2021 · Updated Sep 17, 2024

Reachable assertion in Zephyr RTOS before 2.6.0 allows physically proximate attackers to interrupt service via a Bluetooth L2CAP K-frame. The l2cap_chan_le_recv() function reads a two-byte SDU length with net_buf_pull_le16() without first verifying that the buffer contains both bytes, so a one-byte field reaches an assertion. Bluetooth proximity and an affected build with assertions enabled are required; the crafted frame interrupts the receiving service without reported confidentiality or integrity impact.

CVSS severity4.3
Medium
EPSS probability0.96%
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 Zephyr RTOS before 2.6.0 allows physically proximate attackers to interrupt service via a Bluetooth L2CAP K-frame. The l2cap_chan_le_recv() function reads a two-byte SDU length with net_buf_pull_le16() without first verifying that the buffer contains both bytes, so a one-byte field reaches an assertion. Bluetooth proximity and an affected build with assertions enabled are required; the crafted frame interrupts the receiving service without reported confidentiality or integrity impact.

The record

CVE
CVE-2021-3454
Published
Oct 19, 2021
Updated
Sep 17, 2024
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-617, CWE-130, T1499
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 19, 2021CVE 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=2.4.0 <unspecified
  2. Affected versionversion=v.2.50 <unspecified

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=2.4.0 <unspecified; version=v.2.50 <unspecified

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.3Zephyr ProjectCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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
CWE-130Improper Handling of Length Parameter Inconsistency
T1499Endpoint Denial of Service

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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