CVE-2025-27840: ESP32 Firmware Hidden HCI Command Flaw

CVE-2025-27840 Overview

Espressif ESP32 chips allow 29 hidden HCI commands, such as 0xFC02 (Write memory).

Critical Impact
The undocumented HCI commands could allow unauthorized memory operations, leading to potential compromise of device integrity and confidentiality. This makes the vulnerability crucial to address in environments leveraging ESP32 for critical operations.

Affected Products

espressif esp32_firmware
espressif esp32

Discovery Timeline

2025-03-08 - CVE CVE-2025-27840 published to NVD
2025-03-12 - Last updated in NVD database

Technical Details for CVE-2025-27840

Vulnerability Analysis

The vulnerability occurs due to 29 undocumented HCI Bluetooth commands that can manipulate device memory. This includes command 0xFC02, which allows unauthorized memory writing, exposing devices to potential data corruption or unauthorized code execution.

Root Cause

The root cause is the inclusion of undocumented HCI commands within the ESP32 firmware that bypass typical security restrictions, allowing low-level memory manipulation.

Attack Vector

Physical access is required to exploit these hidden HCI commands.

// Example pseudo code for memory writing command
void exploitCommand()
{
    int hciCommand = 0xFC02; // Write memory command
    int memoryAddress = 0x12345678;
    int data = 0xDEADBEEF; // Example data
    executeHCICommand(hciCommand, memoryAddress, data);
}

Detection Methods for CVE-2025-27840

Indicators of Compromise

Unusual memory access logs
Unauthorized Bluetooth HCI command execution traces
Unexpected firmware behavior or crashes

Detection Strategies

Leveraging behavioral analysis tools to track Bluetooth communication and using anomaly detection algorithms to identify undocumented HCI command executions.

Monitoring Recommendations

Regularly monitor logs for exotic HCI commands and set alerts for any use of command 0xFC02 and related undocumented actions. Integrate SentinalOne’s AI-driven detection to flag suspicious behaviors indicative of attempted exploitations.

How to Mitigate CVE-2025-27840

Immediate Actions Required

Disable undocumented HCI commands by applying vendor patches
Restrict physical access to devices
Regularly update to the latest firmware

Patch Information

Espressif has not released an official patch yet. It is advised to check ESP32's vendor advisory channels for future updates.

Workarounds

Consider implementing strict access controls and monitoring Bluetooth traffic to detect anomalous command usage.

bash

# Example configuration to disable HCI commands
hci-tools disable 0xFC02