CVE-2026-80782 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
HID: magicmouse: do not keep a stale msc->input if no input is claimed
magicmouse_input_mapping() caches the first hid_input's input_dev in msc->input while the report descriptor is parsed, and the rest of the driver treats a non-NULL msc->input as proof that an input device was registered.
That does not hold on the hid-input error path. If hidinput_connect() fails -- for instance because input_register_device() returns an error -- it unwinds through hidinput_disconnect(), which frees every input_dev it created, including the one cached in msc->input.
The failure does not abort the probe. hid_connect() only skips the claim:
if ((connect_mask & HID_CONNECT_HIDINPUT) && !hidinput_connect(hdev, connect_mask & HID_CONNECT_HIDINPUT_FORCE)) hdev->claimed |= HID_CLAIMED_INPUT;
and the "device has no listeners" bailout below it does not fire for this driver, which sets ->raw_event; on the USB Magic Mouse 2 / Magic Trackpad 2 paths hidraw and hiddev are claimed as well. hid_hw_start() therefore returns 0 and magicmouse_probe() continues with msc->input pointing at freed memory. Being non-NULL, it passes the "input not registered" check in probe and the NULL checks in ->raw_event and ->event, so the next input report dereferences freed memory.
Clear msc->input when the HID core did not claim an input device, so the existing NULL checks cover this case as well.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified within the Linux kernel's HID magicmouse driver represents a classic use-after-free condition arising from improper state management during hardware initialization and error handling sequences. The root cause lies in how the driver caches references to input device structures without adequately validating their lifecycle status against potential failure paths in the underlying HID subsystem. Specifically, the function magicmouse_input_mapping() stores a pointer to an hid_input's input_dev structure within the msc->input field while parsing the report descriptor. This cached reference is subsequently used by other parts of the driver as a definitive indicator that an input device has been successfully registered and remains valid for interaction.
The critical flaw manifests when the connection process encounters an error, particularly during the invocation of hidinput_connect(). If this function fails due to issues such as input_register_device() returning an error code, the HID core initiates an unwind sequence via hidinput_disconnect(). This cleanup routine correctly frees all allocated input_dev structures, including the specific one that was cached in msc->input. However, the probe logic for the magicmouse driver does not abort execution upon this failure. Instead, it relies on a conditional check regarding whether the HID_CONNECT_HIDINPUT flag is set and whether hidinput_connect succeeded to determine if the device should be claimed as an input device.
Due to the specific implementation details of the magicmouse driver, which sets the ->raw_event callback, the standard bailout mechanism for devices with no listeners does not trigger. Furthermore, on USB Magic Mouse 2 and Magic Trackpad 2 paths, hidraw and hiddev interfaces are also claimed successfully even if the input interface fails. Consequently, hid_hw_start() returns a success status of zero, causing magicmouse_probe() to continue its execution flow under the false assumption that all resources are valid. The driver proceeds with msc->input pointing to memory that has already been freed by the disconnect routine.
This stale pointer leads directly to a use-after-free vulnerability when subsequent input reports arrive and trigger the ->raw_event or ->event callbacks. Because these functions perform only basic NULL checks on msc->input, they fail to detect that the pointed-to structure is no longer valid memory allocated to another context or freed entirely. Dereferencing this dangling pointer results in undefined behavior, which can lead to kernel crashes, data corruption, or potentially arbitrary code execution if an attacker can influence the contents of the freed memory region through heap spraying techniques or other exploitation methods.
From a classification perspective, this vulnerability aligns with CWE-416 Use After Free and CWE-362 Race Condition involving shared resources without proper synchronization, although in this specific case it is more accurately described as a logic error leading to use-after-free rather than a traditional timing race. In the context of the MITRE ATT&CK framework for Linux systems, this flaw could be leveraged during privilege escalation phases where an attacker exploits kernel memory corruption to gain higher-level access or disrupt system stability. The failure lies in the lack of robust state validation after asynchronous or error-prone subsystem calls return control to the driver probe routine.
To mitigate this vulnerability, it is essential to ensure that cached pointers are invalidated immediately when their associated resources are released. As indicated by the resolution, clearing msc->input when the HID core does not claim an input device ensures that existing NULL checks in the ->raw_event and ->event handlers correctly identify the absence of a valid input structure. This simple fix prevents dereferencing freed memory by forcing the driver to treat the unclaimed state as equivalent to no input device being present. Developers should implement similar defensive programming practices across all HID drivers, ensuring that any cached references are explicitly nullified during error paths and disconnect routines to maintain consistency between resource allocation status and pointer validity. Regular static analysis and code reviews focusing on lifecycle management of kernel objects can further prevent such logic errors in future development cycles.