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Esp IdfApplication · Espressif

CVE-2021-28139

HIGH · 8.8 CVSS v3.1 Published 2021-09-07
Fix available
A fix is available. Upgrade to after 4.4 or later.
See remediation →
93/100
Remediation priority · Urgent
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The Bluetooth Classic implementation in Espressif ESP-IDF 4.4 and earlier does not properly restrict the Feature Page upon reception of an LMP Feature Response Extended packet, allowing attackers in radio range to trigger arbitrary code execution in ESP32 via a crafted Extended Features bitfield payload.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The ESP-IDF Bluetooth Classic stack fails to properly validate the Feature Page in LMP Feature Response Extended packets. When an ESP32 receives a crafted Extended Features bitfield payload from a nearby attacker, the malformed input can be processed in an unsafe manner, leading to arbitrary code execution on the device.

MitigationUpdate ESP-IDF to a version newer than 4.4 that contains the proper bounds checking on Feature Page values in LMP Feature Response Extended packets, then rebuild and deploy updated firmware to all affected ESP32 devices.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Esp IdfApplication
Affected:<= 4.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm ESP-IDF is the firmware framework
    Check your build system, firmware documentation, or examine the firmware image for ESP-IDF markers. Look for the ESP-IDF version string in the firmware binary or check your project's IDF_PATH or version.h headers.
    Affected if The device does not use ESP-IDF as its framework, then this CVE does not apply.
  2. Identify the installed ESP-IDF version
    Run 'git log' in your ESP-IDF directory, check the version tag in the IDF environment (idf.py --version), or look for version indicators in your firmware build artifacts. Compare the version to the affected range: any version <= 4.4 is affected.
    Affected if The ESP-IDF version is 4.4 or lower.
  3. Verify Bluetooth Classic (BR/EDR) is enabled
    Check your project configuration (sdkconfig or menuconfig) for CONFIG_BT_BLUEDROID_ENABLED=y and verify that Bluetooth Classic support is not disabled. Look for CONFIG_BT_CLASSIC_ENABLED or similar Bluetooth Classic configuration options.
    Affected if Bluetooth Classic (BR/EDR) is enabled in the firmware configuration.
  4. Confirm the device uses the legacy LMP Feature Response Extended handler
    Review the ESP-IDF Bluetooth stack source code in your firmware or IDF installation. The vulnerability exists in the LMP feature response extended packet handler within the classic Bluetooth stack. Check if your build includes the Bluetooth controller and stack components.
    Affected if The firmware includes the ESP-IDF Bluetooth Classic stack handling LMP packets.

A device is affected if it runs ESP-IDF version 4.4 or lower with Bluetooth Classic (BR/EDR) enabled, as the vulnerability resides in the LMP Feature Response Extended packet processing path.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 4.4
Interim mitigation

Update ESP-IDF to a version newer than 4.4 that contains the proper bounds checking on Feature Page values in LMP Feature Response Extended packets, then rebuild and deploy updated firmware to all affected ESP32 devices.

Recommended fix Moderate confidence

ESP-IDF v4.4.1 or later stable release

  1. 1. Identify the current ESP-IDF version in use by checking with 'idf.py --version' or reviewing project configuration
  2. 2. Download the latest stable ESP-IDF release from the official Espressif repository at https://github.com/espressif/esp-idf
  3. 3. Install the updated ESP-IDF version following the standard installation process for your operating system
  4. 4. Update the ESP-IDF environment by running the install script (install.sh or install.bat) and activating the environment (export.sh or export.bat)
  5. 5. Clean and rebuild existing projects to ensure the new ESP-IDF components are used
  6. 6. Rebuild and redeploy firmware to ESP32 devices
Caveat Review release notes for any breaking changes between v4.4 and the target upgrade version; Bluetooth stack modifications may affect existing classic Bluetooth functionality

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Esp Idf Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-28139 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data