CVE-2026-89620
Summary
by MITRE • 09/11/2026
In the Linux kernel, the following vulnerability has been resolved:
HID: intel-thc-hid: intel-quickspi: validate report size before copy
write_cmd_to_txdma() builds an output report in qsdev->report_buf, a heap buffer allocated in quickspi_alloc_report_buf() to the device-descriptor derived max_report_len (a few hundred bytes for a touch controller). It copies the caller-supplied report into that buffer:
memcpy(write_buf->content, report_buf, report_buf_len);
The HID core caps a report at HID_MAX_BUFFER_SIZE (16384) by default, and quickspi_hid_ll_driver does not set max_buffer_size, so the length reaches the driver unbounded. A hidraw SET_REPORT/SET_FEATURE ioctl carrying a report larger than max_report_len therefore overflows report_buf with attacker-controlled length and content.
Record the report_buf allocation size and reject reports that do not fit before copying, matching the equivalent guard in the intel-quicki2c sibling (quicki2c_init_write_buf()) and the hid-goodix-spi fix.
write_cmd_to_txdma() writes the output report header ahead of the content in the same buffer, so size the allocation to cover the header as well. That keeps the added bound from rejecting a maximum-sized report.
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Analysis
by VulDB Data Team • 09/11/2026
The Linux kernel vulnerability identified within the HID Intel THC driver involves a heap-based buffer overflow caused by insufficient validation of input data lengths during command processing. The core issue resides in the write_cmd_to_txdma function, which is responsible for constructing output reports destined for hardware devices such as touch controllers. This function utilizes a heap-allocated buffer named report_buf, sized according to max_report_len derived from device descriptors, typically ranging only a few hundred bytes. However, when copying user-supplied report data into this fixed-size buffer using memcpy, the driver fails to verify that the incoming report size does not exceed the allocated capacity. This lack of boundary checking creates a direct path for memory corruption if an attacker can supply oversized payloads.
The root cause of this vulnerability is linked to how the HID core subsystem manages buffer sizes and how specific drivers interact with it. By default, the HID core caps reports at HID_MAX_BUFFER_SIZE, which equals 16384 bytes. The quickspi_hid_ll_driver implementation does not explicitly set a max_buffer_size limit for its operations. Consequently, when an application interacts with the device via hidraw using SET_REPORT or SET_FEATURE ioctls, it can request to write data up to this large default limit. Since the driver allocates report_buf based on the smaller hardware-specific max_report_len rather than the HID core's maximum allowed size, any input exceeding that smaller threshold results in a buffer overflow. This discrepancy allows an attacker-controlled length and content to overwrite adjacent memory structures beyond the bounds of report_buf.
The operational impact of this vulnerability is severe due to its potential for arbitrary code execution or denial of service. A successful exploitation could allow a local user with access to the hidraw interface to corrupt kernel heap memory, potentially leading to privilege escalation if the overwritten data includes function pointers or control structures used by subsequent operations. Furthermore, because write_cmd_to_txdma writes an output report header ahead of the content within the same buffer, improper sizing can also affect how headers are parsed later in the processing pipeline, further complicating exploitation mitigation and increasing instability risks for system stability.
To mitigate this vulnerability, developers must implement strict size validation before performing memory copy operations. Specifically, the allocation logic should record the exact size of report_buf and reject any incoming reports that exceed this limit prior to copying data into it. This approach mirrors existing safeguards found in sibling drivers such as quicki2c_init_write_buf and hid-goodix-spi, ensuring consistency across similar hardware interfaces. Additionally, since write_cmd_to_txdma writes headers before content within the same buffer, allocation sizes must account for both header and payload to prevent off-by-one errors or partial overflows when handling maximum-sized reports. These changes align with CWE-120 standards regarding buffer copy without checking size limits and address ATT&CK techniques related to local privilege escalation through memory corruption vulnerabilities in kernel drivers.