CVE-2026-80769 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
HID: rapoo: fix missing hid_is_usb() check
to_usb_interface() can only be used on a hid_device whose parent is really USB; uhid can create devices that identify as being on BUS_USB, but don't actually have a USB parent. Fix the use of to_usb_interface() without a hid_is_usb() check.
Add a dependency on USB_HID for hid_is_usb(), as other HID drivers do; the alternative would be to provide a simple stub implementation on !USB_HID builds.
I have verified that it is currently possible to trigger a kernel splat due to this bug in an ASAN build, and that this commit fixes the issue.
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Analysis
by VulDB Data Team • 09/08/2026
The Linux kernel's Human Interface Device subsystem contains a logic flaw within the Rapoo wireless mouse driver that stems from an incorrect assumption about device topology. The function to_usb_interface is designed exclusively for use with hid_device structures whose parent hardware interface is physically connected via USB. However, the uhid virtual HID driver allows user-space applications to create synthetic devices that report their bus type as BUS_USB without actually possessing a real USB physical parent structure. When the Rapoo driver processes such a device, it proceeds to call to_usb_interface on this invalid context because it fails to verify whether the device is genuinely attached via USB before attempting the cast. This oversight leads to dereferencing an incorrect or non-existent pointer within the kernel memory space, resulting in undefined behavior that manifests as a kernel splat or crash during runtime operations involving these virtual devices.
From a technical perspective, this vulnerability represents a classic case of improper input validation and type confusion where software assumes a specific structural relationship exists without verifying it at execution time. The absence of a prior check using hid_is_usb allows the code path to proceed under false premises regarding memory layout and object validity. In environments configured with AddressSanitizer or similar debugging tools, this flaw is readily reproducible as the sanitizer detects the out-of-bounds access or invalid pointer dereference immediately upon invocation. This confirms that the bug is not merely theoretical but actively exploitable in scenarios where an attacker can control device creation through uhid interfaces, potentially leading to denial of service conditions by crashing the kernel subsystem responsible for handling input devices.
The operational impact of this vulnerability primarily centers on system stability and availability rather than direct privilege escalation or data exfiltration. An unprivileged local user with access to create virtual HID devices via uhid can trigger a kernel panic or oops, effectively disrupting all connected USB-based human interface peripherals until the system is rebooted. While the immediate effect is a denial of service, such instability in core input handling layers can have cascading effects on desktop environments and server applications that rely heavily on consistent keyboard and mouse inputs for operation. The lack of proper boundary checking means that any process capable of interacting with uhid can destabilize the entire kernel HID subsystem, impacting system reliability significantly.
To mitigate this risk, the resolution involves adding a mandatory check using hid_is_usb before invoking to_usb_interface within the Rapoo driver code path. This ensures that the cast is only performed when the device structure genuinely corresponds to a USB interface object, thereby preventing invalid memory access. Additionally, the patch introduces a dependency on the USB_HID configuration option for this specific driver, aligning its build requirements with other HID drivers in the kernel tree. This architectural adjustment prevents compilation issues or runtime failures in configurations where USB support is disabled by ensuring that the necessary helper functions are available only when appropriate subsystems are enabled. Users should apply the corresponding kernel update to restore proper validation logic and eliminate the possibility of triggering this crash condition through virtual device manipulation.
This vulnerability aligns with CWE-20, which describes improper input validation, as the driver failed to adequately verify that an external entity's data met expected structural constraints before processing it. Furthermore, in terms of attack patterns, this scenario relates to ATT&CK technique T1564, specifically hiding execution or modifying system processes via kernel-level instability, although more directly it reflects flaws often associated with CWE-823, which covers the use of objects outside their valid scope. The fix reinforces the principle that drivers must rigorously validate device properties against actual hardware topology before performing type-specific operations, ensuring robustness across both physical and virtual HID implementations within the Linux kernel environment.