CVE-2019-19194 : Exploit Details and Defense Strategies

A potential security vulnerability has been identified in the implementation of the Bluetooth Low Energy Secure Manager Protocol (SMP) on Telink Semiconductor BLE SDK versions released before November 2019. This vulnerability affects TLSR8x5x through 3.4.0, TLSR823x through 1.3.0, and TLSR826x through 3.3 devices. The issue arises when an out-of-order link-layer encryption request is received during the process of Secure Connections pairing. In such cases, the implementation inadvertently sets a zero long term key (LTK). Exploiting this vulnerability, an attacker within radio range can gain unauthorized read/write access to protected GATT service data, potentially causing a device crash or even manipulating the device's functionalities by establishing an encrypted session with the zero LTK.

Understanding CVE-2019-19194

This section provides an overview of the CVE-2019-19194 vulnerability.

What is CVE-2019-19194?

The CVE-2019-19194 vulnerability is a security flaw in the Bluetooth Low Energy Secure Manager Protocol (SMP) implementation on Telink Semiconductor BLE SDK versions released before November 2019. It allows an attacker to exploit the zero long term key (LTK) set during Secure Connections pairing, leading to unauthorized access and potential device manipulation.

The Impact of CVE-2019-19194

The vulnerability poses the following risks:

Unauthorized read/write access to protected GATT service data
Device crashes
Manipulation of device functionalities through an encrypted session with the zero LTK

Technical Details of CVE-2019-19194

This section delves into the technical aspects of CVE-2019-19194.

Vulnerability Description

The vulnerability occurs in the Bluetooth Low Energy Secure Manager Protocol (SMP) implementation on Telink Semiconductor BLE SDK versions released before November 2019. It results from the incorrect handling of out-of-order link-layer encryption requests during Secure Connections pairing, leading to the installation of a zero long term key (LTK).

Affected Systems and Versions

TLSR8x5x through 3.4.0
TLSR823x through 1.3.0
TLSR826x through 3.3

Exploitation Mechanism

An attacker within radio range can exploit the vulnerability by establishing an encrypted session with the zero LTK, gaining unauthorized read/write access to GATT service data and potentially causing device malfunctions.

Mitigation and Prevention

This section outlines steps to mitigate and prevent exploitation of CVE-2019-19194.

Immediate Steps to Take

Update affected Telink Semiconductor BLE SDK versions to releases after November 2019
Implement network segmentation to limit exposure
Monitor for any unauthorized access attempts

Long-Term Security Practices

Regularly update firmware and software to patch known vulnerabilities
Conduct security assessments and penetration testing
Educate users and employees on secure Bluetooth practices

Patching and Updates

Apply patches provided by Telink Semiconductor for the affected SDK versions
Stay informed about security updates and advisories from relevant sources