CVE-2018-20787 in perseus-p-oss MIX 3
Summary
by MITRE
The ft5x46 touchscreen driver for custom Linux kernels on the Xiaomi perseus-p-oss MIX 3 device through 2018-11-26 has an integer overflow and OOPS because of missing checks of the size argument in tpdbg_write in drivers/input/touchscreen/ft5x46/ft5x46_ts.c. This is exploitable for a device crash via a syscall by a crafted application on a rooted device.
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Analysis
by VulDB Data Team • 07/19/2023
The CVE-2018-20787 vulnerability resides within the ft5x46 touchscreen driver implementation for Linux kernels running on Xiaomi MIX 3 devices, specifically affecting versions through 2018-11-26. This flaw manifests as an integer overflow condition that leads to a kernel oops event, fundamentally compromising system stability and potentially enabling further exploitation. The vulnerability is rooted in insufficient validation of input parameters within the tpdbg_write function located in drivers/input/touchscreen/ft5x46/ft5x46_ts.c, where the size argument lacks proper boundary checks during kernel space operations.
The technical implementation of this vulnerability involves a critical flaw in input validation where the driver fails to properly verify the size parameter passed to the tpdbg_write function. When a malicious application crafts a specific payload with an oversized size argument, the integer overflow occurs during arithmetic operations within the kernel space, resulting in unpredictable memory access patterns. This condition directly violates the fundamental principles of secure coding practices as outlined in CWE-190, which addresses integer overflow vulnerabilities. The overflow causes the kernel to access memory beyond allocated boundaries, triggering an immediate system crash or oops event that terminates the device's touchscreen functionality and potentially destabilizes other kernel components.
From an operational perspective, this vulnerability creates a significant attack surface for privilege escalation scenarios, particularly when exploited by a crafted application running on a rooted device. The exploitability requires local privileges but does not necessitate network access, making it particularly dangerous in environments where device rooting has already occurred. The impact extends beyond simple denial of service to potentially enabling more sophisticated attacks that could leverage the kernel crash to gain additional privileges or access to sensitive system resources. This aligns with ATT&CK technique T1068 which covers 'Exploitation for Privilege Escalation' and demonstrates how kernel-level vulnerabilities can be weaponized to bypass security controls. The vulnerability essentially creates a pathway for attackers to cause persistent system instability while maintaining operational control over the device.
The mitigation strategies for CVE-2018-20787 should focus on implementing robust input validation within the kernel driver code, specifically adding proper bounds checking for the size argument in the tpdbg_write function. System administrators should ensure timely patching of kernel versions containing the vulnerable driver implementation, with particular attention to devices running custom Xiaomi firmware. Security monitoring should include detection of anomalous kernel oops events and unusual memory access patterns that could indicate exploitation attempts. Additionally, device manufacturers should implement proper kernel hardening measures including stack canaries, address space layout randomization, and kernel address space protection features to reduce the overall attack surface. The vulnerability highlights the importance of comprehensive kernel security testing and the need for proper code review processes that validate all input parameters within kernel space drivers.