CVE-2025-66409 is an out-of-bounds read vulnerability classified under CWE-125 found in the Espressif Internet of Things Development Framework (ESP-IDF), specifically affecting the Bluetooth stack on ESP32 devices when the Audio/Video Remote Control Profile (AVRCP) is enabled. The issue arises because the Bluetooth stack processes VENDOR DEPENDENT commands from peer devices without adequately validating the length of the command buffer before accessing it. This improper validation allows the stack to read memory outside the intended buffer bounds, potentially exposing sensitive memory contents or causing unexpected behavior such as crashes or data leakage. The vulnerability affects multiple ESP-IDF versions, including 5.1.6 and all versions up to 5.5.1, as well as their respective beta releases. Exploitation requires an attacker to send a malformed VENDOR DEPENDENT command over Bluetooth to a vulnerable ESP32 device with AVRCP enabled. No authentication or user interaction is necessary, making remote exploitation feasible within Bluetooth range. However, the impact is limited to information disclosure or stability issues, with no known privilege escalation or code execution vectors. No public exploits have been reported to date. The CVSS v4.0 score is 2.7, reflecting low severity due to the limited impact and attack complexity. The vulnerability highlights the importance of robust input validation in embedded Bluetooth stacks, especially in IoT frameworks widely used in consumer and industrial devices.

For European organizations, the impact of CVE-2025-66409 is generally low but context-dependent. Organizations deploying ESP32-based IoT devices with Bluetooth AVRCP enabled—such as smart home devices, industrial sensors, or consumer electronics—may face risks of unintended memory disclosure or device instability if targeted by attackers within Bluetooth range. Although the vulnerability does not allow remote code execution or privilege escalation, information leakage could aid attackers in further reconnaissance or targeted attacks. Critical infrastructure sectors using ESP32 devices in operational technology environments might be more sensitive to device reliability issues caused by unexpected behavior. However, the limited attack surface (Bluetooth proximity required) and low severity reduce the overall risk. Still, organizations with large-scale IoT deployments should consider the cumulative risk and potential for chained exploits. The absence of known exploits in the wild suggests limited current threat activity, but proactive mitigation is advisable to prevent future exploitation.

To mitigate CVE-2025-66409, European organizations should: 1) Monitor Espressif's official channels for patches addressing this vulnerability and plan timely updates to ESP-IDF versions beyond 5.5.1 once available. 2) If immediate patching is not feasible, disable AVRCP functionality on ESP32 devices where it is not required to eliminate the attack vector. 3) Implement Bluetooth device access controls and network segmentation to limit exposure of vulnerable devices to untrusted Bluetooth peers. 4) Employ Bluetooth monitoring tools to detect anomalous or malformed VENDOR DEPENDENT commands indicative of exploitation attempts. 5) For critical deployments, conduct security assessments of ESP32 device firmware and Bluetooth stack configurations to ensure no additional vulnerabilities are present. 6) Educate operational teams on the risks associated with Bluetooth-enabled IoT devices and enforce policies restricting unauthorized Bluetooth connections. These targeted measures go beyond generic advice by focusing on the specific vulnerability vector and device configurations.