Undocumented Hidden Commands in Espressif ESP32 Bluetooth Chips

CVE-2025-27840

What is CVE-2025-27840?

CVE-2025-27840 is a vulnerability found in Espressif ESP32 Bluetooth chips, which are widely used in various Internet of Things (IoT) devices and applications. The ESP32 chips facilitate Bluetooth and Wi-Fi connectivity, making them essential for smart devices. This vulnerability pertains to the presence of 29 undocumented hidden HCI commands, including commands that could allow unauthorized actions such as writing to memory. If exploited, this vulnerability could severely compromise the integrity and security of devices employing ESP32 chips, placing organizations at risk of unauthorized access and control over critical systems.

Technical Details

The vulnerability revolves around undocumented hidden HCI (Host Controller Interface) commands available in Espressif ESP32 Bluetooth chips. Notably, one of these commands, 0xFC02, enables the writing of memory on the device. The presence of such hidden commands raises significant security concerns, as they could potentially facilitate various unauthorized operations without being detected by standard security protocols. This situation underscores the risks associated with using devices that have undocumented functionalities, which may not have undergone rigorous security assessments.

Potential Impact of CVE-2025-27840

1. Unauthorized Access: The hidden commands can provide malicious actors with the ability to bypass standard security measures, leading to unauthorized access to devices and systems that utilize ESP32 chips.

2. Data Manipulation: Exploitation of this vulnerability could allow attackers to manipulate or alter data stored on affected devices. This could compromise the integrity of operational data, which is critical for decision-making in connected systems.

3. Porous Security Posture: As this vulnerability exposes IoT devices to potential takeover, it significantly undermines the overall security posture of organizations that rely on these devices for their operations, especially in sectors where security and data integrity are paramount.

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