CVE-2024-40984 is a vulnerability identified in the Linux kernel's ACPICA (ACPI Component Architecture) subsystem. The issue stems from a flawed handling of memory mappings for operation regions in ACPI, specifically related to how the kernel manages memory regions that cross page boundaries. A previous commit (d410ee5109a1) attempted to prevent warnings caused by mapping multiple Base Address Registers (BARs) by restricting memory mappings to not cross page boundaries. However, this fix introduced a critical flaw: when a memory mapping request spans a boundary but only a partial mapping is made (e.g., a 4-byte request but only 1 byte mapped due to page boundary limits), the kernel still attempts to read or write the full requested length. This results in a NULL pointer dereference, causing a kernel crash or denial of service. The correct approach, as per the ACPI specification, is to allow mappings that span multiple page boundaries, mapping the entire requested length rather than truncating at a boundary. This vulnerability can lead to system instability or crashes when the kernel attempts invalid memory accesses during ACPI operations. While no known exploits are currently in the wild, the flaw resides in a fundamental kernel subsystem that is widely used across Linux distributions, making it a significant concern for systems relying on ACPI for hardware configuration and power management.

For European organizations, the impact of CVE-2024-40984 can be substantial, particularly for those operating critical infrastructure, data centers, or enterprise environments running Linux-based systems. The vulnerability can cause kernel panics or system crashes, leading to denial of service conditions. This can disrupt business operations, cause downtime, and potentially affect availability of services. In environments where uptime and reliability are critical, such as financial institutions, healthcare providers, and manufacturing plants, such disruptions can have cascading effects on operational continuity and compliance with regulatory requirements. Additionally, while this vulnerability does not directly lead to privilege escalation or data breaches, denial of service attacks can be leveraged as part of multi-stage attacks or to distract security teams. Given the widespread use of Linux in servers, cloud infrastructure, and embedded systems across Europe, the potential attack surface is broad. Organizations using customized or older kernel versions that include the problematic commit are particularly at risk until patches are applied.

To mitigate CVE-2024-40984, organizations should: 1) Apply the latest Linux kernel updates that revert the problematic commit and restore correct ACPICA memory mapping behavior. Since the vulnerability is due to a recent kernel commit, updating to the latest stable kernel version or vendor-provided patches is critical. 2) Conduct an inventory of Linux systems to identify those running affected kernel versions containing commit d410ee5109a1. 3) For systems where immediate kernel updates are not feasible, consider isolating or limiting access to vulnerable systems to reduce exposure. 4) Monitor system logs and kernel messages for signs of NULL pointer dereference crashes or ACPI-related errors, which may indicate exploitation attempts or instability. 5) Engage with Linux distribution vendors and maintain awareness of security advisories to ensure timely patch deployment. 6) In environments using custom kernels, review and test kernel patches carefully to avoid reintroducing the flawed behavior. 7) Implement robust backup and recovery procedures to minimize impact from potential denial of service incidents.