Realtek Vulnerability Allows DoS Attack via Bluetooth Pairing

A critical denial-of-service vulnerability in Realtek’s RTL8762E SDK v1.4.0 that affects Bluetooth Low Energy (BLE) secure connections.

The vulnerability allows attackers to disrupt the pairing process by exploiting improper state machine validation, potentially rendering affected devices unable to establish secure BLE connections.

The vulnerability specifically targets the RTL8762EKF-EVB development platform and stems from the SDK’s failure to enforce proper message ordering during the Bluetooth Secure Connections pairing sequence.

The vulnerability, discovered in the RTL8762EKF-EVB development platform, represents a significant security vulnerability in Realtek’s BLE implementation.

Security researchers found that the affected SDK accepts Pairing Random packets before the required Pairing Public Key exchange, directly violating the Bluetooth Core Specification’s mandated protocol flow.

This premature acceptance creates a state machine violation that causes the entire pairing process to fail.

The impact extends beyond simple connection failures. Attackers can repeatedly exploit this vulnerability to maintain persistent denial of service, effectively blocking all legitimate BLE secure connection attempts.

Since the attack requires no special privileges and can be conducted over-the-air within BLE range, it poses a significant threat to IoT devices and embedded systems using the affected SDK.

The vulnerability is particularly concerning for development platforms and production devices that rely on secure BLE connections for critical operations.

Realtek Vulnerability

The root cause lies in the BLE stack’s inadequate protocol state validation mechanisms.

According to the Bluetooth Core Specification v5.3, the Secure Connections pairing process requires strict message ordering where Pairing Random messages must only be processed after successful Pairing Public Key exchange.

However, the RTL8762E SDK v1.4.0 fails to implement this critical validation step.

Key Technical Details:

• BLE stack lacks proper protocol state validation mechanisms.
• SDK fails to enforce Bluetooth Core Specification v5.3 message ordering requirements.
• Pairing Random messages accepted before mandatory Pairing Public Key exchange.
• State machine violation triggers undefined internal state transitions.
• Protocol inconsistency causes immediate pairing process abortion.

Attack Implementation Methods:

• Modified BLE central devices with custom firmware.
• Custom Android stack implementations with protocol manipulation.
• Specialized tools like NRF BLE sniffers with packet injection capabilities.
• Simple three-step process reliably triggers vulnerability.
• Minimal technical sophistication required for successful exploitation.

Mitigations

Security experts recommend immediate implementation of strict state validation mechanisms within the BLE SMP (Security Manager Protocol) layer.

The primary fix involves ensuring that Pairing Random messages are only accepted after both communicating parties have successfully exchanged Pairing Public Keys, as mandated by the Bluetooth specification.

Additional recommended mitigations include implementing proper out-of-sequence message handling by discarding messages that arrive outside their expected protocol position.

Development teams should also consider adding comprehensive logging and debug output capabilities to help identify and diagnose out-of-sequence messages during testing phases.

Find this Story Interesting! Follow us on LinkedIn and X to Get More Instant Updates.