CVE-2024-26977 is a vulnerability identified in the Linux kernel related to the handling of memory-mapped I/O (MMIO) mappings. Specifically, the issue arises from incorrect conditional compilation directives (#ifdef ARCH_HAS_GENERIC_IOPORT_MAP) that inadvertently also guard the iounmap() function call. The iounmap() function is responsible for unmapping previously mapped MMIO regions. Due to this misplaced guard, MMIO mappings are not properly unmapped, resulting in a resource leak. Over time, this leak can lead to exhaustion of kernel resources associated with MMIO mappings, potentially causing system instability or crashes. The vulnerability does not directly impact confidentiality or integrity but affects availability by causing denial of service conditions. The CVSS v3.1 base score is 5.5 (medium severity), reflecting that exploitation requires local access with low privileges (PR:L), no user interaction, and low attack complexity. The scope is unchanged, and the impact is limited to availability (A:H) with no confidentiality or integrity impact. No known exploits are currently reported in the wild. The affected versions are specific Linux kernel commits identified by their hashes, indicating that this is a recent and targeted fix in the kernel source. This vulnerability is relevant to any Linux system utilizing MMIO, which includes a broad range of server, desktop, and embedded systems. The fix involves adjusting the conditional compilation to ensure iounmap() is always called for MMIO mappings, preventing the leak.

For European organizations, the impact of CVE-2024-26977 primarily concerns system stability and availability. Organizations running Linux-based infrastructure—such as servers, network appliances, and embedded devices—may experience degraded performance or unexpected system crashes if the vulnerability is exploited or triggered unintentionally. This can disrupt critical services, especially in sectors relying heavily on Linux servers like finance, telecommunications, healthcare, and public administration. Although the vulnerability does not allow unauthorized data access or modification, denial of service conditions can lead to operational downtime, affecting business continuity and potentially causing financial losses. The requirement for local access and low privileges limits remote exploitation risks, but insider threats or compromised accounts could leverage this vulnerability. Systems with heavy MMIO usage, such as those interfacing with specialized hardware or virtualization environments, are at higher risk of impact. Given the widespread use of Linux in European data centers and critical infrastructure, timely patching is essential to maintain service reliability.

European organizations should prioritize updating their Linux kernels to versions that include the patch for CVE-2024-26977. Since the vulnerability stems from a kernel source code issue, applying official kernel updates from trusted Linux distributions is the most effective mitigation. Organizations should: 1) Identify all Linux systems, especially those with hardware interfacing via MMIO, and verify kernel versions against patched releases. 2) Deploy kernel updates during scheduled maintenance windows to minimize disruption. 3) For systems where immediate patching is not feasible, monitor system logs and resource usage for signs of MMIO mapping leaks or instability. 4) Limit local access to trusted users and enforce strict privilege management to reduce the risk of exploitation by low-privilege users. 5) Employ kernel hardening and security modules (e.g., SELinux, AppArmor) to restrict unauthorized code execution and access. 6) Maintain robust incident response plans to quickly address any denial of service incidents. 7) Engage with hardware vendors and Linux distribution maintainers to ensure compatibility and timely patch availability. These steps go beyond generic advice by focusing on the specific nature of the vulnerability and its exploitation requirements.