CVE-2019-19196 in BLE SDK
Summary
by MITRE
The Bluetooth Low Energy Secure Manager Protocol (SMP) implementation on Telink Semiconductor BLE SDK versions before November 2019 for TLSR8x5x through 3.4.0, TLSR823x through 1.3.0, and TLSR826x through 3.3 devices accepts a pairing request with a key size greater than 16 bytes, allowing an attacker in radio range to cause a buffer overflow and denial of service (crash) via crafted packets.
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Analysis
by VulDB Data Team • 03/30/2024
The vulnerability identified as CVE-2019-19196 represents a critical buffer overflow flaw within the Bluetooth Low Energy Secure Manager Protocol implementation of Telink Semiconductor's BLE SDK. This issue affects multiple device families including TLSR8x5x, TLSR823x, and TLSR826x series, with affected versions released prior to November 2019. The flaw exists in the pairing request handling mechanism where the system fails to properly validate the key size parameter during the Bluetooth LE security negotiation process. This improper validation creates a condition where an attacker positioned within radio range can exploit the vulnerability by transmitting specially crafted pairing requests containing key data exceeding the expected 16-byte limit. The technical implementation error stems from inadequate input validation and buffer management within the SMP stack, which directly relates to CWE-121, heap-based buffer overflow, and CWE-122, stack-based buffer overflow, depending on the specific memory layout during execution. The vulnerability operates at the transport layer of the Bluetooth protocol stack, specifically targeting the security manager protocol which governs the establishment of secure connections between Bluetooth devices. When a malformed pairing request is received, the system's insufficient bounds checking allows the oversized key data to overwrite adjacent memory regions, leading to unpredictable behavior and ultimately system crash or denial of service condition. This type of vulnerability falls under the ATT&CK technique T1059.007 for command and scripting interpreter and T1499.004 for network disruption, as it enables an attacker to disrupt the normal operation of BLE-enabled devices within range. The operational impact is significant for any IoT devices or embedded systems utilizing these Telink Semiconductor chips, as the vulnerability can be exploited without requiring authentication or physical access to the target device. The attack surface is particularly concerning given that Bluetooth Low Energy devices are commonly deployed in security-sensitive applications such as smart locks, medical devices, and industrial control systems where denial of service could result in operational failures or security breaches. The vulnerability demonstrates a fundamental flaw in the security protocol implementation where the system assumes that legitimate pairing requests will adhere to expected parameter sizes without proper validation. The affected device families represent a substantial portion of embedded Bluetooth solutions used in various commercial and industrial applications, making this vulnerability particularly dangerous as it affects devices that may be deployed in critical infrastructure environments. The memory corruption resulting from this buffer overflow can lead to complete system crashes, requiring device reboot or manual intervention to restore normal operation. From a security perspective, this vulnerability represents a failure in the principle of least privilege and input validation, where the system does not properly sanitize incoming data before processing. The exploitability is high due to the proximity requirement being minimal, typically within standard Bluetooth range of 10-100 meters depending on device configuration, making it accessible to attackers in physical proximity to target devices. The lack of proper bounds checking in the SMP implementation creates a persistent threat that can be repeatedly exploited to maintain denial of service conditions, potentially leading to extended operational disruptions. Organizations utilizing these devices should prioritize immediate firmware updates to address this vulnerability, as the attack vector requires no specialized tools beyond standard Bluetooth monitoring equipment. The vulnerability also highlights the importance of robust input validation in embedded security protocols and demonstrates how seemingly minor implementation flaws can lead to significant operational impacts in IoT environments. This issue exemplifies the challenges inherent in securing embedded systems where resource constraints often lead to simplified security implementations that may contain fundamental flaws in protocol handling and data validation. The remediation requires firmware updates that implement proper bounds checking for key size parameters in pairing requests, ensuring that any oversized data is either rejected or properly truncated before processing. The vulnerability serves as a reminder of the critical importance of security testing in embedded systems and the necessity of implementing comprehensive input validation mechanisms even in resource-constrained environments.