CVE-2024-25076 in SmartBond DA14691
Summary
by MITRE • 07/10/2024
An issue was discovered on Renesas SmartBond DA14691, DA14695, DA14697, and DA14699 devices. The bootrom function responsible for validating the Flash Product Header directly uses a user-controllable size value (Length of Flash Config Section) to control a read from the QSPI device into a fixed sized buffer, resulting in a buffer overflow and execution of arbitrary code.
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Analysis
by VulDB Data Team • 07/11/2024
The vulnerability identified as CVE-2024-25076 affects Renesas SmartBond DA14691, DA14695, DA14697, and DA14699 microcontroller devices, representing a critical security flaw in the bootrom implementation that directly impacts device initialization and system integrity. This issue stems from improper input validation within the Flash Product Header validation mechanism, where the system fails to adequately verify user-controllable parameters before executing memory operations. The vulnerability specifically manifests when the bootrom processes the Length of Flash Config Section field, which serves as a critical input parameter for determining how much data to read from the QSPI device during the boot process. The flaw creates a dangerous condition where an attacker can manipulate this length value to cause the system to read more data than the allocated buffer can accommodate, leading to a classic buffer overflow scenario.
The technical execution of this vulnerability occurs through a fundamental flaw in the bootrom's memory management approach, where the system directly uses a user-controllable size parameter to determine the amount of data to read from the QSPI flash memory device. When the Length of Flash Config Section value exceeds the bounds of the fixed-size buffer allocated for reading this data, the overflow condition is triggered, causing adjacent memory locations to be overwritten with attacker-controlled data. This buffer overflow creates an execution path where arbitrary code can be loaded and executed within the device's memory space, effectively allowing an attacker to bypass the normal boot process and gain control over the device's operation. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and more specifically with CWE-787, which addresses out-of-bounds write vulnerabilities that occur when a buffer is written beyond its allocated bounds.
The operational impact of this vulnerability is severe and far-reaching, particularly for IoT devices and embedded systems that rely on these Renesas microcontrollers for secure boot operations and device authentication. Attackers exploiting this vulnerability can potentially gain persistent access to devices, allowing them to modify firmware, extract sensitive data, or establish backdoor access points that persist through device reboots. The vulnerability is particularly concerning because it occurs during the boot process, meaning that even if a device has proper security measures in place during runtime, these protections can be bypassed entirely through manipulation of the bootrom's memory handling. This creates a fundamental weakness in the device's security architecture, as the boot process represents the critical point where device integrity and authenticity are established. The attack vector requires physical access to the device or the ability to inject malicious firmware through legitimate update channels, making it a significant concern for supply chain security and device lifecycle management.
Mitigation strategies for this vulnerability must address both the immediate security risk and the underlying architectural flaw in the bootrom implementation. The primary recommendation involves updating the device firmware to a version that properly validates the Length of Flash Config Section parameter before using it to determine buffer read operations. This validation should include bounds checking to ensure that the specified length does not exceed the maximum buffer capacity and that the data being read from QSPI flash remains within expected parameters. Additionally, implementing proper input sanitization and parameter validation within the bootrom code will prevent the use of user-controllable values in direct memory operations. Security measures should also include monitoring for unauthorized firmware updates and implementing secure boot mechanisms that verify the integrity of all boot components before execution. Organizations should consider adopting defense-in-depth strategies that include network segmentation, anomaly detection, and regular security assessments to identify potential exploitation attempts. The vulnerability demonstrates the critical importance of proper input validation in embedded systems and aligns with ATT&CK technique T1542.001, which covers the use of boot or logon initialization scripts to gain persistence, as the attacker can potentially establish persistent access through this bootrom vulnerability.