CVE-2026-42805 in BHI385 SensorAPI
Summary
by MITRE • 09/10/2026
A stack-based buffer overflow vulnerability exists in the Bosch Sensortec BHI385 SensorAPI (C library) within the debug message parser function bhi385_parse_debug_message (located in bhi385_parse.c).
The function parses FIFO events and extracts an 8-bit message length directly from the attacker-controlled event payload (callback_info->data_ptr[0]) without enforcing bounds checks or clamping the value.
When copying the payload into a fixed-size stack buffer of 17 bytes (uint8_t debug_msg[17]) via memcpy, providing a length byte greater than 16 causes the function to write past the allocated stack boundary.
This memory corruption can be triggered by a malicious or compromised sensor or bus participant, leading to a firmware crash, Denial of Service (DoS), or potentially the execution of arbitrary code via adjacent stack data corruption.
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Analysis
by VulDB Data Team • 09/10/2026
The vulnerability identified in the Bosch Sensortec BHI385 SensorAPI represents a critical security flaw rooted in improper input validation and memory management practices within the firmware's debug message parsing logic. Specifically, the function bhi385_parse_debug_message, located in the source file bhi385_parse.c, is responsible for processing FIFO events that contain sensor data or diagnostic information. The core technical deficiency lies in how this function handles the length field of incoming messages. It extracts an eight-bit message length value directly from the first byte of the attacker-controlled event payload, specifically at callback_info->data_ptr[0], without performing any bounds checking or clamping operations to ensure the value remains within safe limits for subsequent memory allocation and copying operations. This lack of validation allows a malicious actor who can inject data into this pipeline to dictate exactly how much stack space will be accessed during the parsing process, effectively bypassing standard safety mechanisms that should prevent out-of-bounds access.
The operational mechanism of exploitation involves the function attempting to copy the payload into a fixed-size local buffer declared as uint8_t debug_msg[17]. This allocation reserves seventeen bytes on the call stack for storing the parsed message content. However, because the length byte is not constrained, providing a value greater than sixteen causes the memcpy operation to write data beyond the allocated boundary of this array. In embedded systems and microcontroller environments where memory layout is often static and tightly packed, writing past the end of a local variable typically overwrites adjacent stack variables or critical control structures such as the return address, saved frame pointer, or other function context information. This constitutes a classic stack-based buffer overflow, which falls under CWE-121: Stack-based Buffer Overflow in standard vulnerability classification taxonomies. The absence of compiler-level protections like stack canaries or non-executable stack pages further exacerbates the risk, although even with such mitigations present, the logical flaw remains exploitable for denial-of-service scenarios if not fully patched by hardware features alone.
The impact of this vulnerability is severe and multifaceted, primarily affecting the availability and integrity of the sensor hub firmware. A successful exploitation can lead to a immediate Denial of Service (DoS) condition where the microcontroller crashes or resets due to corrupted stack memory, disrupting all connected sensors and system functionality. More critically, if an attacker gains control over the instruction pointer through precise overwrite techniques, they may achieve arbitrary code execution on the device. This scenario aligns with ATT&CK technique T1059: Command and Scripting Interpreter in contexts where script-like firmware modules are involved, or more broadly with privilege escalation vectors that allow lateral movement within a constrained IoT ecosystem. Given that sensor hubs often act as gateways between physical sensors and main application processors, compromising this component could provide an attacker with deep access to the system's internal state, potentially leading to data exfiltration or manipulation of critical sensing inputs used for safety-critical applications such as automotive navigation or industrial monitoring systems.
Mitigation strategies must address both immediate code-level fixes and broader architectural defenses. The primary remediation involves modifying the bhi385_parse_debug_message function to enforce strict bounds checking on the extracted length byte before any memory copy operation occurs. Developers should clamp the value of callback_info->data_ptr[0] to a maximum of sixteen bytes, ensuring that it never exceeds the size of the debug_msg buffer minus one for null termination if applicable. Additionally, implementing input validation at earlier stages in the FIFO event processing pipeline can prevent malformed packets from reaching this vulnerable function altogether. From an architectural perspective, enabling hardware-based memory protection features such as Memory Protection Units (MPUs) or Stack Canaries where supported by the microcontroller architecture can mitigate the impact of buffer overflows by detecting and terminating unauthorized memory accesses before they lead to code execution. Regular security audits focusing on embedded C code patterns that involve dynamic length fields should also be conducted to identify similar vulnerabilities across other sensor APIs, ensuring a holistic approach to firmware security resilience against supply chain or physical interface attacks.