CVE-2017-8072 in Linux
Summary
by MITRE
The cp2112_gpio_direction_input function in drivers/hid/hid-cp2112.c in the Linux kernel 4.9.x before 4.9.9 does not have the expected EIO error status for a zero-length report, which allows local users to have an unspecified impact via unknown vectors.
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Analysis
by VulDB Data Team • 08/25/2024
The vulnerability identified as CVE-2017-8072 resides within the Linux kernel's HID (Human Interface Device) subsystem, specifically in the cp2112_gpio_direction_input function located in drivers/hid/hid-cp2112.c. This function is responsible for managing GPIO (General Purpose Input/Output) direction control for devices using the Silicon Labs CP2112 HID-to-serial bridge chip. The affected kernel versions span from 4.9.0 through 4.9.8, making this a significant issue that impacts a substantial portion of the kernel 4.9.x release line. The vulnerability manifests when the function processes zero-length reports, which are typically used in HID communication to indicate device state or control commands.
The technical flaw stems from the improper handling of error conditions within the cp2112_gpio_direction_input function. When a zero-length report is received, the function fails to return the expected EIO error status that would indicate a communication failure or invalid data condition. This deviation from standard error handling protocols creates a potential security boundary issue where malformed or unexpected HID reports could bypass normal validation mechanisms. The function's inability to properly signal error conditions means that the kernel's HID subsystem may continue processing potentially invalid data without proper error indication, leading to unpredictable behavior in the GPIO control operations.
The operational impact of this vulnerability extends beyond simple error handling, as it provides local users with an unspecified but potentially significant attack surface. Local privilege escalation remains a primary concern since attackers with access to the system could exploit this weakness to manipulate GPIO operations in ways that were not intended by the kernel's design. The unspecified impact suggests that various system behaviors could be affected, potentially including denial of service conditions, data corruption in GPIO-controlled peripherals, or even privilege escalation to root-level access depending on how the GPIO operations are integrated with other system components. This vulnerability particularly affects embedded systems and devices that rely heavily on HID communication for device control and configuration.
The vulnerability aligns with CWE-248, which addresses "Uncaught Exception" in software systems, as the function fails to properly handle the exceptional case of zero-length reports. Additionally, this weakness can be categorized under ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation" by providing an entry point for local users to gain elevated privileges. The issue also relates to the broader category of input validation failures that can lead to unexpected system behavior and potential security breaches. Organizations should note that this vulnerability is particularly dangerous in embedded environments where the CP2112 chip is commonly used for USB-to-serial communication and GPIO control in industrial and IoT devices. The fix for this vulnerability required updating the kernel to version 4.9.9 or later, which properly implements the expected error handling for zero-length HID reports. System administrators should prioritize patching affected systems and monitor for any unusual GPIO behavior that might indicate exploitation attempts. The vulnerability demonstrates the importance of robust error handling in kernel subsystems and the potential consequences when standard error conditions are not properly implemented.