CVE-2020-13594 in ESP-IDF
Summary
by MITRE
The Bluetooth Low Energy (BLE) controller implementation in Espressif ESP-IDF 4.2 and earlier (for ESP32 devices) does not properly restrict the channel map field of the connection request packet on reception, allowing attackers in radio range to cause a denial of service (crash) via a crafted packet.
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Analysis
by VulDB Data Team • 08/31/2020
The vulnerability identified as CVE-2020-13594 represents a critical flaw in the Bluetooth Low Energy controller implementation within Espressif ESP-IDF versions 4.2 and earlier, specifically affecting ESP32 devices. This issue stems from inadequate validation of the channel map field within connection request packets, creating a pathway for remote attackers to exploit the system through crafted Bluetooth packets transmitted within radio range. The flaw exists at the hardware abstraction layer level where the BLE controller processes incoming connection requests, demonstrating a fundamental weakness in input validation mechanisms that should have been implemented to prevent malformed data from causing system instability.
The technical execution of this vulnerability occurs when an attacker constructs a malicious connection request packet containing an invalid or improperly formatted channel map field. When the ESP32 device receives this crafted packet, the BLE controller fails to properly validate the channel map data, leading to memory corruption or unexpected behavior that ultimately results in a system crash or complete denial of service. This represents a classic buffer overread or invalid memory access scenario where the controller attempts to process data beyond expected boundaries, causing the device to become unresponsive and requiring manual intervention or power cycling to restore functionality. The vulnerability operates at the link layer of the Bluetooth protocol stack, specifically affecting the connection establishment process where the controller must parse and validate incoming connection parameters before accepting or rejecting connection attempts.
The operational impact of this vulnerability extends beyond simple service disruption, as it fundamentally compromises the reliability and availability of BLE-enabled ESP32 devices in deployed environments. In IoT applications where these devices serve as critical communication endpoints, such as smart home systems, industrial sensors, or medical devices, a successful attack could lead to complete system outages, data loss, or failure to maintain critical communication channels. The remote nature of the attack means that adversaries do not require physical access to the device or network privileges, making the vulnerability particularly concerning for applications where devices operate in uncontrolled environments. This flaw directly violates security principles outlined in CWE-129 and CWE-131 categories, which address improper input validation and buffer overflow conditions respectively, and aligns with ATT&CK techniques related to denial of service and privilege escalation through protocol manipulation.
Mitigation strategies for this vulnerability require immediate attention from device manufacturers and system administrators, with the most effective approach being the upgrade to Espressif ESP-IDF version 4.3 or later, which includes proper validation of the channel map field in connection requests. Additionally, network administrators should implement physical security measures to prevent unauthorized Bluetooth access within radio range of critical devices, though this approach provides only partial protection. The implementation of proper input validation mechanisms within the BLE controller firmware serves as the primary defense, ensuring that all incoming connection request packets undergo rigorous validation before any processing occurs. Organizations should also consider network segmentation and monitoring solutions to detect anomalous Bluetooth traffic patterns that might indicate exploitation attempts, while maintaining regular firmware update schedules to address similar vulnerabilities that may emerge in the future.