Espressif ESP32, Hidden HCI Command Execution, CVE-2025-27840 (Critical)

The CVE-2025-27840 vulnerability affects Espressif ESP32 chips, which are widely used in IoT devices. This vulnerability allows attackers to execute 29 hidden HCI (Host Controller Interface) commands, such as the command 0xFC02 (Write memory). These commands are not documented and can be exploited to write arbitrary data to memory locations, potentially leading to code execution, privilege escalation, or device compromise. The issue arises due to insufficient access control mechanisms in the firmware, which fails to restrict access to these hidden commands. Attackers can exploit this vulnerability by sending specially crafted HCI packets to the target device, bypassing security checks and gaining unauthorized control over the system. This vulnerability is particularly critical in IoT environments where ESP32 chips are used, as it can lead to full device takeover and potential network compromise.

DailyCVE Form:

Platform: Espressif ESP32
Version: All firmware versions
Vulnerability: Hidden HCI Command Execution
Severity: Critical
Date: 03/08/2025

What Undercode Say:

Exploitation:

Attackers can craft malicious HCI packets targeting the ESP32 chip.
Use the hidden command 0xFC02 to write arbitrary data to memory.
Exploit the lack of access control to execute malicious code.

Protection:

Update firmware to the latest version provided by Espressif.
Implement access control mechanisms to restrict HCI commands.
Monitor network traffic for unusual HCI packet patterns.

Analytics:

CVSS Score: 9.8 (Critical)
Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Commands:

1. To check firmware version:

esptool.py --port /dev/ttyUSB0 flash_id

2. To update firmware:

esptool.py --port /dev/ttyUSB0 write_flash 0x1000 firmware.bin

Code Snippet for Exploit Detection:

import socket
def detect_hci_exploit(packet):
if packet.startswith(b'\xFC\x02'):
return "Potential CVE-2025-27840 Exploit Detected"
return "Safe"

Code Snippet for Protection:

def validate_hci_command(command):
allowed_commands = [bash] Example allowed commands
if command not in allowed_commands:
return "Blocked: Unauthorized HCI Command"
return "Allowed"

Mitigation Steps:

1. Disable unused HCI interfaces.

Use secure boot to prevent unauthorized firmware updates.

3. Regularly audit device logs for suspicious activity.

References:

Espressif Security Advisory: [bash]
NVD CVE-2025-27840: [bash]
MITRE CVE Database: [bash]

References:

Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-27840
Extra Source Hub:
Undercode

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