A newly discovered set of undocumented commands in the widely used ESP32 microcontroller has raised significant cybersecurity concerns, with potential risks spanning consumer electronics, industrial control systems, and critical infrastructure. This vulnerability, now officially tracked under CVE-2025-27840, could allow cybercriminals to manipulate memory, impersonate devices, and inject malicious code into millions of IoT devices.
🔍 Discovery of a “Backdoor-Like” Hidden Feature
At the RootedCON cybersecurity conference, Tarlogic Security unveiled their research into the ESP32 chip, which is manufactured by Espressif and deployed in a vast array of IoT devices, from smart home appliances to medical equipment.
Researchers discovered 29 undocumented commands within the ESP32 firmware, which enable:
- Memory manipulation (read/write operations in RAM and Flash storage).
- MAC address spoofing, allowing malicious actors to impersonate trusted devices.
- LMP/LLCP packet injection, which can be used for Bluetooth and NFC-based attacks.
These capabilities raise the alarming possibility of covert cyber intrusions, where attackers can bypass security mechanisms and implant persistent malware into vulnerable devices.
🚨 Why Is This Vulnerability Dangerous?
The ESP32 chip is a low-cost, mass-market microcontroller used in millions of IoT devices worldwide. Since its launch, over one billion units have been sold, making this vulnerability a high-impact threat.
🛠️ Exploitation Scenarios
The hidden commands discovered by Tarlogic could be leveraged by cybercriminals to conduct a wide range of sophisticated attacks, including:
1️⃣ Persistent Malware Infections
- Malicious actors could use these hidden commands to inject firmware-level malware that persists across reboots and firmware updates.
- This could lead to mass-scale botnets, remote surveillance, or long-term compromise of IoT devices.
2️⃣ Device Impersonation & Identity Theft
- MAC address spoofing allows attackers to masquerade as legitimate devices.
- This means an attacker could impersonate a trusted device (e.g., a corporate laptop, smartphone, or medical sensor) to gain unauthorized access to sensitive networks.
3️⃣ Industrial Espionage & Critical Infrastructure Attacks
- Many industrial automation systems, smart grid meters, and healthcare devices integrate ESP32 for Bluetooth/WiFi connectivity.
- Exploiting this vulnerability could allow attackers to manipulate sensor data, disrupt industrial processes, or extract confidential business intelligence.
4️⃣ Supply Chain Risks
- If hardware manufacturers unknowingly ship devices with these vulnerabilities, the risk extends to millions of end-users.
- This could facilitate nation-state espionage, where adversaries use compromised ESP32-based devices to infiltrate supply chains.
📌 CVE-2025-27840: Official Vulnerability Tracking
Following Tarlogic’s disclosure, this vulnerability has been officially cataloged under CVE-2025-27840. The lack of documentation from Espressif raises questions about the origin of these commands:
- Were these features intentionally implemented but undocumented for proprietary reasons?
- Were they mistakenly left accessible due to oversight in firmware development?
- Could they have been introduced as a covert backdoor, either deliberately or unintentionally?
Currently, Espressif has not issued a public response or security update, further exacerbating concerns in the cybersecurity community.
🔍 How Can Organizations Mitigate This Risk?
Given the widespread adoption of ESP32 across industries, cybersecurity professionals must act proactively to mitigate potential threats. Here are key steps organizations can take:
🔹 1. Conduct Immediate Security Audits
Organizations relying on ESP32-based devices should initiate comprehensive security reviews to identify exposure to CVE-2025-27840.
- Bluetooth Security Audits: Utilizing tools like BluetoothUSB, an open-source framework released by Tarlogic, can help security teams test and analyze Bluetooth device vulnerabilities.
- Firmware Analysis: Reverse-engineering and analyzing ESP32 firmware can help detect hidden commands and unauthorized memory modifications.
🔹 2. Implement Network Segmentation
- IoT devices should not have unrestricted access to critical networks.
- Implement strict firewall rules and segregate IoT systems from sensitive business infrastructure.
🔹 3. Enforce Device Authentication & Encryption
- Enforce MAC address whitelisting to prevent impersonation attacks.
- Use end-to-end encryption in Bluetooth and WiFi communication to mitigate packet injection risks.
🔹 4. Stay Updated on Firmware Patches
Until Espressif releases an official firmware patch, users and enterprises should:
- Monitor security advisories from Espressif and Tarlogic.
- Ensure regular firmware updates for all IoT devices.
⏳ What Comes Next?
Tarlogic Security has indicated that further technical details on this vulnerability will be released in the coming weeks. In the meantime, pressure is mounting on Espressif to: ✅ Provide a transparent disclosure on why these hidden commands exist.
✅ Release a firmware patch or mitigation guidance for affected devices.
✅ Collaborate with security researchers to ensure future chips do not contain undocumented functionalities.
With ESP32 chips deeply embedded in modern IoT infrastructure, this security flaw serves as a critical reminder of the urgent need for robust cybersecurity measures in hardware design and IoT deployments.
⚠️ Final Takeaway
The presence of undocumented commands in mass-market microcontrollers like the ESP32 is not just a technical oversight—it is a potential cyberweapon. Whether these commands were intentionally included or an accidental remnant, the risk they pose is severe and widespread.
🔹 If you use ESP32-based devices, take immediate security precautions.
🔹 If you are a manufacturer, conduct a thorough review of your firmware and supply chain security.
🔹 If you are a security researcher, stay engaged as more details emerge.
Cybersecurity is a collective responsibility, and the discovery of CVE-2025-27840 highlights the ongoing challenges in securing the ever-expanding landscape of IoT technology
Information security specialist, currently working as risk infrastructure specialist & investigator.
15 years of experience in risk and control process, security audit support, business continuity design and support, workgroup management and information security standards.