CVE-2021-47134 is a vulnerability identified in the Linux kernel related to the handling of the Flattened Device Tree (FDT) during the early boot process, specifically within the EFI (Extensible Firmware Interface) initialization code. The vulnerability arises in the setup_arch() function, which calls efi_init() and subsequently efi_get_fdt_params(). If no valid FDT is found, the initial_boot_params pointer becomes null. However, the kernel code did not properly halt further FDT processing in this scenario, which could lead to a kernel panic. This issue was notably observed on the RISC-V architecture, where the absence of a valid FDT triggers the panic. The FDT is critical for describing hardware layout to the kernel at boot time, and improper handling of its absence can cause system instability or denial of service. Although this vulnerability does not appear to have an associated CVSS score and no known exploits are reported in the wild, it represents a stability and availability risk for affected Linux systems, particularly those running on RISC-V or similar architectures where FDT usage is common. The vulnerability was resolved by adding a check to stop further FDT processing when no valid FDT is found, preventing the kernel panic.

For European organizations, the primary impact of CVE-2021-47134 is on system availability and stability. Systems running Linux kernels affected by this vulnerability may experience unexpected kernel panics during boot if the FDT is missing or invalid, leading to denial of service conditions. This could disrupt critical infrastructure, embedded systems, or servers that rely on Linux, especially those using RISC-V or other architectures where FDT is essential. While the vulnerability does not directly compromise confidentiality or integrity, the resulting downtime could affect business operations, service availability, and potentially lead to financial losses or reputational damage. Organizations deploying Linux in embedded devices, industrial control systems, or cloud environments with custom kernel builds should be particularly cautious. Since no known exploits exist, the immediate threat level is moderate, but unpatched systems remain vulnerable to accidental or intentional triggering of the kernel panic.

To mitigate this vulnerability, European organizations should: 1) Apply the latest Linux kernel updates and patches that address CVE-2021-47134, ensuring the fix that halts FDT processing when no valid FDT is found is included. 2) Validate the presence and correctness of the FDT in their boot configurations, especially for RISC-V and other affected architectures, to prevent boot-time failures. 3) Implement robust monitoring and alerting for kernel panics or boot failures to enable rapid response. 4) For embedded or specialized Linux deployments, conduct thorough testing of boot sequences with various FDT configurations to detect potential issues early. 5) Maintain an inventory of Linux kernel versions in use across infrastructure to identify and prioritize vulnerable systems for patching. 6) Consider fallback or recovery mechanisms such as bootloader configurations that can recover from failed boots caused by this issue.