CVE-2021-47405 is a vulnerability identified in the Linux kernel's USB Human Interface Device (usbhid) driver. The issue pertains to improper memory management where raw_report buffers, which are used to handle input reports from USB HID devices, are not freed correctly when a device is removed. This results in a memory leak, as the unsent raw_report buffers remain allocated even after the device is disconnected. The vulnerability was discovered and reported by the syzbot fuzzing system, which is an automated tool designed to find bugs in the Linux kernel. The fix involves explicitly freeing these raw_report buffers during the usbhid_stop routine, ensuring that memory is properly released when the device is removed. The affected versions are identified by a specific commit hash, indicating that this vulnerability impacts certain kernel builds prior to the patch. There are no known exploits in the wild targeting this vulnerability, and no CVSS score has been assigned yet. The vulnerability primarily affects the availability aspect of the system by causing a memory leak, which over time could degrade system performance or lead to denial of service if the kernel runs out of memory due to unreleased buffers. The vulnerability does not appear to require user interaction or authentication to be triggered, but it does require the presence of USB HID devices and their removal to trigger the memory leak condition.

For European organizations, the impact of CVE-2021-47405 is primarily related to system stability and availability. Many European enterprises and public sector entities rely heavily on Linux-based systems for servers, workstations, and embedded devices. USB HID devices such as keyboards, mice, and specialized input devices are ubiquitous in these environments. A memory leak in the kernel's handling of these devices could lead to gradual degradation of system performance, increased memory consumption, and potentially system crashes or reboots if the leak is severe and sustained. This could disrupt critical business operations, especially in sectors like finance, manufacturing, healthcare, and government services where uptime and reliability are essential. Although no direct confidentiality or integrity risks are evident, the availability impact could indirectly affect operational continuity and service delivery. Since the vulnerability does not require active exploitation or user interaction beyond device removal, it could be triggered inadvertently during routine hardware changes or device failures, making it a concern for IT administrators managing large fleets of Linux systems.

To mitigate CVE-2021-47405, European organizations should prioritize applying the official Linux kernel patches that address the memory leak in the usbhid driver. This involves updating to a kernel version that includes the fix, which frees raw_report buffers upon device removal. Organizations should maintain a robust patch management process to ensure timely deployment of kernel updates across all affected systems. Additionally, monitoring system memory usage and kernel logs for unusual patterns related to USB device handling can help detect potential memory leaks early. For environments with critical uptime requirements, consider implementing automated system restarts or memory reclamation strategies as a temporary mitigation until patches are applied. IT teams should also review USB device usage policies to minimize unnecessary device removals or replacements that could trigger the leak. Finally, maintaining an inventory of Linux kernel versions in use and their patch status will assist in risk assessment and prioritization of remediation efforts.