CVE-2021-47659 is a vulnerability identified in the Linux kernel's Direct Rendering Manager (DRM) subsystem, specifically within the plane initialization function __drm_universal_plane_init(). The issue arises from the improper placement of a range check for the variable format_count, which represents the number of supported pixel formats for a DRM plane. The check is intended to ensure that format_count does not exceed 64, a limit presumably set to prevent resource over-allocation or logic errors. However, in the vulnerable code, this check occurs after the allocation of the plane->format_types array and other associated resources. If format_count exceeds 64, the check triggers a WARN_ON (a kernel warning), but because it is placed late, the function leaks the allocated plane->format_types array and fails to call drm_mode_object_unregister(), which is responsible for cleaning up and unregistering the modeset identifier. This sequence results in resource leakage and potentially inconsistent kernel state. The fix involves moving the range check to the start of the function, preventing allocation and registration of resources when format_count is invalid, thereby avoiding the leak and ensuring proper cleanup. Although the vulnerability does not appear to be exploitable for code execution or privilege escalation directly, it can lead to resource leaks within the kernel's DRM subsystem, which might degrade system stability or availability over time. There are no known exploits in the wild, and no CVSS score has been assigned to this vulnerability. The affected versions are specific Linux kernel commits identified by their hashes, indicating that this is a recent or in-development patch. The vulnerability is technical and subtle, primarily affecting systems using the DRM subsystem for graphics plane management.

For European organizations, the impact of CVE-2021-47659 is primarily related to system stability and resource management on Linux systems utilizing the DRM subsystem, which is common in servers, desktops, and embedded devices with graphical capabilities. While the vulnerability does not directly enable remote code execution or privilege escalation, the resource leak could lead to gradual degradation of system performance or availability, especially in environments with high graphics workload or frequent plane initialization operations. This could affect sectors relying on Linux-based infrastructure for graphics-intensive applications, such as media production, scientific visualization, or industrial control systems. The impact is more pronounced in environments where uptime and reliability are critical, as resource leaks in kernel space can cause subtle memory exhaustion or kernel object leaks leading to crashes or degraded performance. However, since there are no known exploits and the vulnerability requires a specific condition (format_count > 64), the immediate risk is moderate. Organizations with robust patch management and monitoring are less likely to be affected. The vulnerability also highlights the importance of kernel updates in maintaining system integrity.

To mitigate CVE-2021-47659, European organizations should: 1) Apply the latest Linux kernel patches that include the fix moving the format_count check earlier in __drm_universal_plane_init(). This is the definitive solution to prevent resource leaks. 2) Monitor kernel logs for WARN_ON messages related to DRM plane initialization, which could indicate attempts to trigger this condition or underlying misconfigurations. 3) Audit and validate any custom or third-party kernel modules interacting with the DRM subsystem to ensure they do not bypass or exacerbate this vulnerability. 4) Implement resource monitoring on systems with heavy graphics workloads to detect abnormal memory or resource consumption patterns that could be symptomatic of this leak. 5) For critical systems, consider isolating or limiting workloads that heavily utilize DRM plane initialization until patches are applied. 6) Maintain a strict kernel update policy, especially for systems exposed to untrusted inputs or running graphical workloads. 7) Engage with Linux distribution vendors for timely updates and advisories related to this vulnerability. These steps go beyond generic advice by focusing on proactive monitoring, workload management, and vendor coordination.