Discovery at Rootedcon: Unveiling the Hidden Commands

the security world buzzed following the proclamation at the Rootedcon conference in madrid, where Miguel Tarascó Acuña and Antonio Vázquez Blanco presented their findings. Their research centered on the ESP32 chip,a product of the Chinese company Espressive,valued for its cost-effectiveness at approximately 2 euros,according too Tarlogic Security. The potential for a security vulnerability in such a ubiquitous component promptly raised concerns. The conference, held between March 6 and 8, served as the platform for this significant security disclosure.

Tarlogic Security announced the discovery in a press release on March 6, stating:

Tarlogic Security has detected a hidden functionality which can be used as a stolen door in ESP32, a microcontroller which allows the Wi-fi and bluetooth connection and which is present in millions of IoT public devices.
Tarlogic security Press release,March 6,2025

The researchers achieved this breakthrough by developing a custom Bluetooth pilot in C,bypassing the standard operating system APIs. This allowed them to directly access raw Bluetooth traffic, revealing 29 hidden commands embedded within the ESP32 chip’s firmware. These commands enable memory manipulation, granting access to sensitive data and allowing for packet injection. The ability to bypass standard APIs and directly interact with the chip’s firmware opened a new avenue for both research and potential exploitation.

Initially labeled as a “stolen door” by Tarlogic, the issue is now tracked under CVE-2025-27840. the vulnerability received a CVSS3.1 severity score of 6.8 out of 10 and is classified as “hidden functionality.” This reclassification has stirred some controversy within the security community,with some experts questioning the initial characterization.

Exploitation Complexity and Potential Risks

Tarlogic Security highlighted the potential risks associated with this discovery:

The exploitation of this hidden functionality would allow opposed players to carry out attacks by usurpation of identity and permanently infect sensitive devices such as mobile phones, computers, bright locks or medical equipment by bypassing audit controls of the code.
Tarlogic Security Press Release

Though, exploiting these hidden commands is not straightforward. It requires low-level access to the target device, either through physical connections like USB or UART, or via a separate attack that grants remote access. This secondary attack would likely involve exploiting another vulnerability, perhaps through malware. The need for multiple layers of access makes exploitation more complex but doesn’t eliminate the potential threat.

If attackers succeed,they could potentially embed persistent malware within the chip’s limited memory,establishing an Advanced Persistent Threat (APT). From there, they could theoretically compromise other devices on the network by re-exploiting the initial vulnerability. The persistent nature of such an attack poses a significant long-term risk to connected devices and networks.

Debate: Stolen Door or Vendor-Specific Commands?

The initial characterization of the hidden functionality as a “stolen door” has faced criticism from some experts. Tarlogic Security has since updated its interaction, referring to the commands as a “hidden function” that can be used “like” a stolen door. This shift in terminology reflects the ongoing debate within the security community.

Xeno Kovah, from Dark Mentor, has voiced strong disagreement with the “stolen door” label, stating:

What researchers highlight (HCI commands specific to the supplier to read and write the memory of the controller) is a common design model found in other Bluetooth chips other suppliers, such as Broadcom, Cypress and Texas Instruments.
Xeno Kovah,Dark Mentor

Kovah argues that these commands are more accurately described as a private API,rather than a backdoor. This outlook suggests that the functionality is intentional and part of the chip’s design, rather than a malicious insertion.

the term “backdoor” typically implies malicious intent and a purposeful attempt to deceive. Dark Mentor points out that the Bluetooth protocol includes a Host Controller Interface (HCI), which facilitates communication between the host device and the Bluetooth chip. While the Bluetooth Core specification defines common commands, it also allows manufacturers to introduce Vendor Specific Commands (VSC). These VSCs are intended for manufacturer-specific functionalities and optimizations.

Dark Mentor also notes that the researchers’ findings were based on reverse engineering of a ROM provided by Espressive on its Github repository,highlighting Espressive’s clarity. This transparency suggests that the commands were not intentionally hidden for malicious purposes.

A Matter of Viewpoint: Weakness vs. Vulnerability

Davi Ottenheimer echoes this sentiment, describing the commands as “owner commands” used for testing and manufacturing, a standard practice. He acknowledges the value of the research in exploring bluetooth security and testing methodologies. This perspective emphasizes the intended use of the commands for legitimate purposes.

This perspective is reflected in the CVE file, which references CWE-912, indicating a “weakness” in the ESP32 chip’s firmware rather than a full-fledged “vulnerability.” A weakness suggests a potential flaw that could be exploited, while a vulnerability implies a known and readily exploitable flaw.

Interviewer (Senior Editor, world-today-news.com): Dr. Anya Sharma,a leading expert in embedded systems security,welcome to world-today-news.com. The recent revelation of hidden commands within the widely used ESP32 chip has sent ripples through the cybersecurity community. Can you shed light on this discovery for our readers?

Dr. Sharma: Thank you for having me. the discovery of these so-called “hidden commands” in the ESP32 microcontroller is indeed a significant event, prompting a crucial discussion about the complexities of embedded systems security and the lines between legitimate functionality and potential vulnerabilities. These commands, accessed through a custom Bluetooth pilot bypassing standard operating system APIs, offer capabilities like memory manipulation and packet injection. While the researchers initially described them as a “stolen door,” a more nuanced viewpoint is needed.

Interviewer: The initial claim of a “stolen door,” implying malicious intent, has been met with counterarguments suggesting these commands are simply vendor-specific, analogous to a private API.What’s your take on this debate?

Dr. Sharma: this highlights a crucial distinction.A “backdoor,” or “stolen door,” implies deliberate malicious placement for unauthorized access. In contrast, vendor-specific commands (VSCs), often part of the Host Controller Interface (HCI), are commonly used by manufacturers for testing, debugging, and specialized functionality. The ESP32 case involves Vendor Specific commands, part of the Bluetooth protocol’s Host Controller Interface (HCI). Many Bluetooth chip manufacturers include such commands, including Broadcom, Cypress and Texas Instruments. The core issue isn’t necessarily about malicious intent but rather about secure implementation and potential misuse of these commands. The key question is not whether these commands exist, but how well-protected they are against unauthorized access.

Understanding the Risks: Exploitation and Mitigation

Interviewer: Let’s delve into the practical implications. How easily can these commands be exploited, and what are the potential consequences for users?

Dr. Sharma: Exploiting these commands requires relatively advanced technical skills and low-level access – either physically via interfaces like USB or UART, or remotely through another vulnerability. This layered attack vector highlights the importance of complete security measures, going beyond simply patching a single vulnerability. Success could lead to several dire outcomes: data breaches,identity theft,and the installation of persistent malware,potentially establishing an advanced persistent threat (APT),which can compromise entire networks.

Interviewer: What steps can individuals and organizations take to mitigate these potential risks associated with the ESP32’s hidden commands and secure their devices?

Dr. Sharma: A layered approach is essential:

• Firmware Updates: Regularly update the firmware of devices utilizing ESP32 chips to address any potential vulnerabilities that may be discovered.
• Network Segmentation: Isolate devices using ESP32 chips within your network, limiting potential damage from compromises.
• Secure Coding Practices: For developers, embracing secure coding practices becomes crucial.Thoroughly validate and test all firmware, minimizing embedded vulnerabilities.
• Regular Security Audits: Conduct periodic security assessments to identify and address potential vulnerabilities in your systems using ESP32,along with other components.
• Principle of Least Privilege: Apply the principle of least privilege to restrict access to essential functionalities and resources, reducing the impact of a potential triumphant attack.
• Incident Response Planning: Develop and regularly maintain a robust incident response plan to effectively deal with any potential security breach, minimizing the disruption and damage.

The Bigger Picture: Embedded System Security

Interviewer: This incident highlights broader concerns in the security of embedded systems. What are some key lessons learned from this case?

Dr. Sharma: This situation reinforces the critical need for clarity and rigorous security testing throughout the entire lifecycle of embedded systems—from design and progress to manufacturing and deployment. Manufacturers need to prioritize security by design, providing sufficient protection to prevent unauthorized access to these frequently enough overlooked functionalities. Open-source initiatives can play a significant role in identifying and addressing vulnerabilities. Additionally, stronger collaboration between researchers, manufacturers, and the wider security community is crucial for advancing the state-of-the-art in embedded systems security.

Interviewer: Dr. Sharma, thank you for providing such clear and insightful perspective on this complex issue. This discussion has been exceptionally valuable.

Dr. Sharma: My pleasure. I hope this helps everyone better understand the nuances of this situation and the importance of proactive security measures in the increasingly interconnected world of the Internet of Things (iot).