CVE-2021-3434

Memory corruption via oversized L2CAP ECRED channel request

Published Jun 28, 2022 · Updated Sep 17, 2024

Stack-based buffer overflow in Zephyr RTOS 2.5.0 through 2.5.x allows physically proximate attackers to corrupt memory via an oversized L2CAP ECRED request. The Bluetooth host's le_ecred_conn_req() handler accepts more than the five permitted channel entries and processes them using fixed-size stack storage without first rejecting the excess. Bluetooth ECRED reachability is required; published evidence establishes stack corruption but does not demonstrate code execution or a specific service failure.

CVSS severity4.9
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in Zephyr RTOS 2.5.0 through 2.5.x allows physically proximate attackers to corrupt memory via an oversized L2CAP ECRED request. The Bluetooth host's le_ecred_conn_req() handler accepts more than the five permitted channel entries and processes them using fixed-size stack storage without first rejecting the excess. Bluetooth ECRED reachability is required; published evidence establishes stack corruption but does not demonstrate code execution or a specific service failure.

The record

CVE
CVE-2021-3434
Published
Jun 28, 2022
Updated
Sep 17, 2024
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-121, CWE-787
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 28, 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=v2.5.0 <unspecified
  2. Affected versionversion=v2.6.0 <unspecified

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=v2.5.0 <unspecified; version=v2.6.0 <unspecified

Published CVSS scores

4.9Zephyr ProjectCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
CWE-787Out-of-bounds Write

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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