CVE-2021-47586 is a medium-severity vulnerability identified in the Linux kernel's network driver subsystem, specifically within the stmmac driver for the DesignWare MAC (dwmac) implementation on Rockchip platforms (rk_gmac). The issue arises from an out-of-bounds (OOB) read in the function rk_gmac_setup. This function iterates over a flexible array member 'regs' within an 'ops' structure using a loop: while (ops->regs[i]) { ... }. However, for many platforms, the 'regs' array is empty, causing the loop to read memory beyond the intended bounds of the structure. Although in practice this often reads zeroed memory, preventing immediate crashes or corruption, it is an unsafe operation that violates memory safety principles and can lead to undefined behavior. The root cause is the absence of a valid 'regs' array, and the fix involves introducing a flag to indicate whether the 'regs' field is valid, thereby avoiding the loop when it is not. This vulnerability is classified under CWE-125 (Out-of-bounds Read). The CVSS v3.1 base score is 5.5 (medium), with vector AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, indicating local attack vector, low complexity, low privileges required, no user interaction, unchanged scope, no confidentiality or integrity impact, but high impact on availability. There are no known exploits in the wild at this time, and no patch links were provided in the source information, but the issue has been resolved in the Linux kernel source. This vulnerability affects Linux kernel versions identified by the commit hash 3bb3d6b1c1957e88bfc5e77a4557f7e6ba761fe3.

For European organizations, the primary impact of CVE-2021-47586 lies in potential denial of service (DoS) conditions on systems running affected Linux kernel versions with the vulnerable stmmac driver enabled, particularly on Rockchip-based hardware platforms. Since the vulnerability causes an out-of-bounds read that can lead to kernel instability or crashes, critical network infrastructure or embedded devices using these drivers may experience unexpected downtime. This can disrupt business operations, especially in sectors relying on embedded Linux devices such as telecommunications, industrial control systems, and IoT deployments prevalent in Europe. However, the vulnerability does not compromise confidentiality or integrity, limiting the risk of data breaches or unauthorized modifications. The requirement for local access and low privileges reduces the likelihood of remote exploitation but does not eliminate risk from insider threats or compromised local accounts. Organizations with extensive use of Rockchip-based Linux systems should be particularly vigilant. Given the medium severity and absence of known exploits, the immediate risk is moderate but warrants proactive patching to maintain system stability and availability.

1. Apply the official Linux kernel patches that address CVE-2021-47586 as soon as they become available from trusted sources or Linux distribution maintainers. 2. For organizations using Rockchip-based embedded devices or network equipment running Linux, verify the kernel version and driver status to identify vulnerable systems. 3. Implement strict access controls to limit local user privileges, reducing the risk of exploitation by low-privileged users. 4. Monitor system logs and kernel crash reports for anomalies that may indicate attempts to trigger the vulnerability. 5. Where possible, isolate critical network infrastructure and embedded devices from untrusted users to minimize local attack vectors. 6. Engage with hardware vendors to confirm firmware and driver updates that incorporate the fix, especially for embedded or IoT devices. 7. Conduct regular vulnerability assessments and penetration tests focusing on local privilege escalation and kernel stability issues to detect latent exploitation attempts. 8. Maintain an up-to-date inventory of Linux kernel versions and affected drivers across the organization to prioritize patching efforts effectively.