CVE-2021-30283 in Snapdragon Consumer IOT
Summary
by MITRE • 01/03/2022
Possible denial of service due to improper handling of debug register trap from user applications in Snapdragon Consumer IOT, Snapdragon Industrial IOT, Snapdragon Mobile
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Analysis
by VulDB Data Team • 01/05/2022
This vulnerability resides in the Snapdragon consumer iot, industrial iot, and mobile product lines where improper handling of debug register traps from user applications can lead to denial of service conditions. The flaw specifically affects the processor's debug subsystem which manages hardware breakpoints and watchpoints through debug registers. When user applications attempt to manipulate these debug registers in certain ways, the system fails to properly validate or handle the trap conditions, potentially causing the processor to enter an unrecoverable state or system crash. The issue stems from inadequate bounds checking and validation mechanisms within the debug register handling code path, allowing malicious or malformed applications to trigger unexpected behavior that disrupts normal system operation. This vulnerability represents a critical weakness in the processor's privilege separation model where user-level applications can inadvertently or deliberately compromise system stability through debug register manipulation.
The technical implementation of this vulnerability involves the processor's debug unit failing to properly manage the transition between user and kernel modes when debug register traps occur. When an application attempts to set or modify debug registers without proper validation, the hardware debug unit does not correctly handle the resulting trap conditions, leading to potential system hangs or forced reboots. The flaw manifests when the processor's debug exception handler does not properly account for all possible debug register states or when it fails to maintain proper processor state during trap handling. This type of vulnerability typically falls under CWE-248, Improper Exception Handling, and more specifically relates to CWE-754, Improper Check for Unusual or Exceptional Conditions, as the system does not properly validate debug register operations. The vulnerability operates at the hardware level within the processor's debug subsystem, making it particularly dangerous as it can affect system stability regardless of the operating system or application layer protections.
From an operational impact perspective, this vulnerability can result in complete system unavailability when exploited by malicious applications or through legitimate software bugs that trigger the debug register trap conditions. The denial of service can be persistent, requiring system reboot to restore normal operation, and may affect critical embedded systems in industrial environments where uptime is essential. Attackers could potentially exploit this vulnerability to create persistent denial of service conditions against devices running affected Snapdragon processors, impacting everything from mobile devices to industrial IoT equipment. The vulnerability's exploitation requires minimal privileges since it operates at the hardware level and can be triggered through normal user application execution, making it particularly concerning for systems where untrusted applications may be present. This aligns with ATT&CK technique T1499.004, Network Denial of Service, and potentially T1059.001, Command and Scripting Interpreter, when malicious code is used to trigger the debug register manipulation.
Mitigation strategies for this vulnerability primarily focus on firmware and software updates from the chipset manufacturer, as the flaw exists at the hardware level within the processor's debug subsystem. System administrators should prioritize applying security patches that address the debug register handling logic and ensure proper validation of debug register operations. Additionally, implementing runtime monitoring for abnormal debug register usage patterns can help detect potential exploitation attempts. Organizations should consider limiting user application access to debug register manipulation capabilities through operating system level controls and privilege management. The vulnerability highlights the importance of proper hardware-level exception handling and the need for comprehensive testing of debug subsystems during processor design and validation phases. Security teams should monitor for reports of system instability or unexpected reboots that could indicate exploitation of this vulnerability, particularly in environments with high-risk applications or untrusted code execution.