CVE-2026-98206 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
Input: cyttsp5 - clamp the HID report size before memcpy
The size field comes from the device and is used as the memcpy() length into response_buf, which is CY_MAX_INPUT bytes.
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Analysis
by VulDB Data Team • 10/07/2026
This vulnerability represents a classic buffer overflow condition within the Linux kernel's input subsystem, specifically affecting the Cypress Touchscreen Protocol 5 driver known as cyttsp5. The core technical flaw lies in the improper validation of data received from external hardware devices before it is processed by memory copy operations. In this specific implementation, the size field extracted from a Human Interface Device report originates directly from the connected peripheral device without sufficient bounds checking against the allocated buffer limits. This lack of input sanitization creates a critical security gap where malicious or malformed HID reports can dictate how much data is copied into the response_buf array.
The operational impact of this flaw is severe, as it allows for potential out-of-bounds writes that could lead to kernel memory corruption. Since the memcpy function uses the device-provided size value directly as its length parameter, an attacker with physical access or control over the input device can supply a report containing a size field larger than CY_MAX_INPUT. This causes the copy operation to write beyond the boundaries of response_buf into adjacent memory regions within the kernel space. Such buffer overflow conditions are particularly dangerous in operating system kernels because they compromise the integrity and stability of the entire system, potentially leading to denial of service through kernel panics or crashes.
From a threat modeling perspective, this vulnerability aligns with CWE-120 Buffer Copy without Checking Size of Input which is classified as a classic buffer overflow. It also relates to CWE-20 Improper Input Validation because the driver fails to verify that incoming data conforms to expected constraints before processing. In terms of adversary tactics, this flaw could be leveraged within an ATT&CK framework context under techniques involving input device manipulation or local privilege escalation if combined with other vulnerabilities to achieve arbitrary code execution. The attack vector is typically physical proximity requiring interaction with the touchscreen interface, making it a localized but high-impact risk for mobile and embedded Linux devices utilizing Cypress touch controllers.
To mitigate this vulnerability, developers must implement strict bounds checking before invoking memory copy functions that rely on external input sizes. Specifically, the size field extracted from the HID report should be compared against CY_MAX_INPUT to ensure it does not exceed the allocated buffer capacity. If the reported size is larger than the maximum allowed value, the driver should either truncate the data to fit within the buffer or reject the malformed report entirely with an appropriate error code. This defensive programming practice ensures that memory operations remain contained within their intended boundaries regardless of malicious input values.
System administrators and users relying on affected kernel versions should prioritize applying security patches provided by their distribution maintainers as soon as they become available. Since this issue resides in a specific driver module, ensuring that the cyttsp5 module is updated to include these validation checks effectively neutralizes the risk. Regular auditing of input handling code within device drivers and adherence to secure coding standards can prevent similar vulnerabilities from being introduced in future kernel releases. Continuous monitoring for updates related to input subsystem components remains essential for maintaining robust security posture on Linux-based devices with touch interfaces.