CVE-2024-46822 is a vulnerability identified in the Linux kernel specifically affecting the arm64 architecture's ACPI (Advanced Configuration and Power Interface) subsystem. The issue arises in the function get_cpu_for_acpi_id(), which is responsible for mapping ACPI CPU IDs to Linux CPU structures. The vulnerability is related to the handling of CPU hotplug events for virtual CPUs (vCPUs) and involves a missing or invalid CPU entry due to improper validation of the Multiprocessor Affinity Register (MPIDR) during the mapping of the GIC (Generic Interrupt Controller) CPU interface. If the MPIDR check fails in the acpi_map_gic_cpu_interface() function, it can result in the cpu_madt_gicc[cpu] array entry being NULL. Subsequent dereferencing of this NULL pointer can cause a kernel NULL pointer dereference, leading to a potential kernel crash (denial of service). Although no known exploit path has been established to trigger this condition, the Linux kernel maintainers have hardened the code to prevent this scenario by enforcing stricter validation and ensuring a valid CPU ID is used for indexing. This vulnerability is subtle and tied to low-level kernel operations managing CPU hotplug and interrupt controller mappings on arm64 systems, which are common in servers, embedded devices, and increasingly in cloud environments using ARM-based infrastructure.

For European organizations, the primary impact of CVE-2024-46822 would be a potential denial of service condition on Linux systems running on arm64 architecture. This could disrupt critical services, especially in environments relying on ARM-based servers or embedded systems such as telecommunications infrastructure, industrial control systems, or cloud providers adopting ARM hardware. While no remote code execution or privilege escalation has been reported, a kernel crash could cause system outages, impacting availability and potentially leading to operational downtime. Organizations with ARM-based Linux deployments in data centers or edge computing environments could face service interruptions. Given the lack of known exploits, the immediate risk is moderate, but the vulnerability highlights the need for vigilance in kernel updates. Confidentiality and integrity impacts are minimal as the flaw does not directly allow unauthorized data access or modification. However, availability degradation in critical infrastructure could have cascading effects on business continuity and service delivery.

European organizations should prioritize updating their Linux kernel to the latest patched versions that include the fix for CVE-2024-46822. Since the vulnerability is in the kernel ACPI arm64 code, kernel upgrades are the primary mitigation. Organizations should: 1) Identify all arm64 Linux systems, including servers, embedded devices, and cloud instances. 2) Apply vendor-provided kernel patches or upgrade to kernel versions released after the vulnerability disclosure date (post-September 2024). 3) For environments where immediate patching is not feasible, implement monitoring for kernel crashes or unusual system reboots that could indicate exploitation attempts. 4) Coordinate with hardware and OS vendors to ensure firmware and kernel compatibility with the patch. 5) Review CPU hotplug and virtualization configurations to minimize exposure, especially in virtualized ARM environments. 6) Incorporate this vulnerability into incident response and vulnerability management workflows to track remediation status. Since no exploit is known, proactive patching and monitoring are the best defenses.