CVE-2021-47583 is a vulnerability identified in the Linux kernel specifically affecting the media subsystem driver for mxl111sf devices. The root cause of the vulnerability is the use of an uninitialized mutex within the mxl111sf_ctrl_msg() function. The mutex, state->msg_lock, was originally initialized in the ->init() function; however, due to the order of function calls in the dvb_usbv2_init() sequence, mxl111sf_ctrl_msg() is invoked during the ->frontend_attach() call before the mutex is properly initialized. This improper initialization sequence leads to potential race conditions or undefined behavior when accessing shared resources protected by the mutex. The fix involved moving the mutex initialization to the ->probe() function for all mxl111sf devices, ensuring that the mutex is initialized before any calls to frontend_attach() and thus before mxl111sf_ctrl_msg() is used. This vulnerability is a logic flaw in driver initialization order rather than a memory corruption or privilege escalation issue. There are no known exploits in the wild, and no CVSS score has been assigned yet. The affected versions correspond to specific Linux kernel commits identified by their hashes, indicating the vulnerability is present in certain kernel versions prior to the patch. The issue was reported by Syzbot, an automated kernel fuzzer, and has been addressed in recent kernel updates.

For European organizations, the impact of CVE-2021-47583 is primarily related to system stability and reliability rather than direct security breaches such as privilege escalation or data leakage. Since the vulnerability involves an uninitialized mutex in a media driver, exploitation could lead to race conditions causing kernel panics, system crashes, or denial of service (DoS) on affected devices. Organizations relying on Linux systems with media hardware using the mxl111sf driver—commonly found in digital TV tuners or similar multimedia devices—may experience service interruptions or degraded performance. While the vulnerability does not directly compromise confidentiality or integrity, availability could be impacted, which is critical for service providers, broadcasters, or any infrastructure relying on continuous media streaming or processing. Given the Linux kernel's widespread use in European data centers, embedded systems, and consumer devices, the vulnerability could affect a broad range of environments if the affected driver is in use. However, the lack of known exploits and the technical nature of the flaw reduce the immediate risk of targeted attacks. Nonetheless, unpatched systems remain vulnerable to potential future exploitation or accidental crashes.

European organizations should prioritize updating their Linux kernel to the latest stable version that includes the patch for CVE-2021-47583. Specifically, ensure that kernel versions incorporate the fix where the mutex initialization is moved to the ->probe() function for mxl111sf devices. System administrators should audit their hardware inventory to identify devices using the mxl111sf driver, such as DVB USB tuners or other media peripherals, and verify their kernel versions. For embedded systems or appliances with limited update capabilities, consider vendor-provided firmware updates or kernel backports. Additionally, implement monitoring for kernel logs to detect unusual crashes or mutex-related errors that could indicate attempts to trigger the vulnerability. Employ strict change management and testing procedures when deploying kernel updates to avoid service disruptions. If immediate patching is not feasible, temporarily disabling or unloading the mxl111sf driver where possible can reduce exposure. Finally, maintain awareness of Linux kernel security advisories and subscribe to relevant mailing lists to receive timely updates on this and related vulnerabilities.