CVE-2024-53406: Espressif ESP-IDF Auth Bypass Vulnerability

CVE-2024-53406 Overview

CVE-2024-53406 affects Espressif ESP-IDF v5.3.0, the official development framework for ESP32 series System-on-Chip devices. The vulnerability stems from insecure permissions in the Bluetooth Low Energy (BLE) reconnection logic. The device reuses the session key from a previous connection during reconnection, enabling attackers to bypass authentication. Espressif chips power millions of consumer and industrial Internet of Things (IoT) devices, expanding the attack surface considerably. The flaw is tracked under [CWE-639] (Authorization Bypass Through User-Controlled Key).

Critical Impact

Attackers within BLE range can bypass authentication by exploiting reused session keys, gaining unauthorized access to paired devices and potentially controlling IoT endpoints built on ESP-IDF v5.3.0.

Affected Products

• Espressif ESP-IDF v5.3.0
• ESP32-based IoT devices built with the vulnerable framework
• BLE-enabled embedded applications using ESP-IDF reconnection routines

Discovery Timeline

• 2025-03-13 - CVE-2024-53406 published to the National Vulnerability Database (NVD)
• 2025-12-31 - Last updated in NVD database

Technical Details for CVE-2024-53406

Vulnerability Analysis

The vulnerability resides in the BLE session management logic of ESP-IDF v5.3.0. During the reconnection phase between a previously paired central and peripheral, the firmware retains and reuses the session key from the prior connection rather than performing a fresh key agreement. An attacker who has observed or captured the prior session can leverage the reused key material to impersonate a legitimate peer.

Because session key reuse defeats the freshness guarantees that BLE security modes are designed to provide, authentication checks during reconnection succeed for an attacker who controls or replays the reused key. The result is authentication bypass without requiring valid pairing credentials at reconnection time.

User interaction is required, typically in the form of an action that triggers reconnection, such as bringing a device back into range. Once exploited, the attacker gains the same authenticated context as a legitimate peer, with high impact on confidentiality, integrity, and availability of the affected device.

Root Cause

The root cause is a design flaw in the reconnection state machine: cached session keys from previous connections are not invalidated or rotated. Secure BLE reconnection should derive fresh keys or enforce Link Layer encryption renegotiation. ESP-IDF v5.3.0 skips that step, treating the cached key as authoritative and leaving the protocol vulnerable to session reuse attacks.

Attack Vector

The attack vector is network-adjacent over BLE radio. An attacker captures or recovers the session key from an earlier session between the target device and a paired peer. When the device enters reconnection, the attacker replays or reuses that key to establish an authenticated link. No privileges are required, attack complexity is low, and exploitation requires user interaction to initiate reconnection. A public proof-of-concept describing the session key reuse condition is referenced in the GitHub PoC Documentation.

No verified exploitation code is provided in this advisory. See the ESP-IDF Repository and the linked PoC documentation for technical specifics on the affected reconnection routines.

Detection Methods for CVE-2024-53406

Indicators of Compromise

• Repeated BLE reconnection events from the same peer address without a fresh pairing exchange in device logs.
• Unexpected authenticated BLE sessions on ESP32 devices that follow a prior disconnection with no key renegotiation traffic.
• Anomalous BLE peer behavior, such as a paired central reconnecting from a different radio fingerprint or signal profile.

Detection Strategies

• Audit ESP-IDF firmware versions across the device fleet and flag any deployment running v5.3.0 with BLE enabled.
• Inspect BLE Host Controller Interface (HCI) logs for reconnections that skip Secure Manager Protocol (SMP) key renegotiation.
• Capture BLE traffic in sensitive environments and correlate session identifiers across reconnections to detect key reuse.

Monitoring Recommendations

• Centralize firmware version inventory for IoT devices and alert on assets running ESP-IDF v5.3.0.
• Monitor wireless intrusion detection sensors for repeated BLE pairing or reconnection anomalies near critical assets.
• Track device behavior baselines and trigger alerts on unauthorized command sequences arriving over BLE.

How to Mitigate CVE-2024-53406

Immediate Actions Required

• Identify all devices and products built on Espressif ESP-IDF v5.3.0 with BLE functionality enabled.
• Restrict BLE pairing to controlled environments to reduce opportunities for session key capture.
• Disable BLE on affected devices where the feature is not required for business function.

Patch Information

At the time of publication, no fixed ESP-IDF version is referenced in the NVD entry for CVE-2024-53406. Monitor the Espressif ESP-IDF Repository and Espressif security advisories for updated releases that address session key reuse in the BLE reconnection path. Once a patched release is available, rebuild affected firmware against the updated framework and deploy through the standard update channel.

Workarounds

• Force fresh pairing for sensitive reconnection events instead of relying on cached session state.
• Implement application-layer authentication on top of the BLE link to validate peer identity independent of link-layer keys.
• Reduce BLE transmit power and operating range to limit adversary proximity opportunities.
• Rotate or clear bonded device records on a defined schedule to invalidate cached session material.

# Configuration example: disable BLE bonding cache reuse in application logic
# Clear stored bonds at boot to force fresh pairing on next reconnection
esp_ble_remove_bond_device(remote_bda);
esp_ble_gap_set_security_param(ESP_BLE_SM_AUTHEN_REQ_MODE, &auth_req, sizeof(uint8_t));