CVE-2024-26987 is a vulnerability identified in the Linux kernel related to a deadlock condition occurring when the hugetlb_optimize_vmemmap feature is enabled. The issue arises specifically in the memory management subsystem, particularly within the handling of huge pages (hugetlb). The vulnerability manifests during hard offline testing of huge pages, where a circular locking dependency leads to a deadlock. The deadlock involves two kernel locks: cpu_hotplug_lock and pcp_batch_high_lock. The kernel attempts to acquire these locks in an order that creates a circular wait condition, causing the system to hang. The detailed kernel stack traces show that the deadlock occurs during operations related to memory failure handling and page poisoning, specifically in the functions __hugetlb_vmemmap_restore_folio, dissolve_free_huge_page, and memory_failure. The deadlock is triggered when a process (e.g., bash) holds multiple locks and attempts to acquire another lock that is already involved in a circular dependency. This can halt kernel operations related to CPU hotplugging and memory failure management. The vulnerability is present in Linux kernel versions prior to the patch that resolved this deadlock scenario. It is important to note that this issue is not related to a security breach such as privilege escalation or information disclosure but rather a stability and availability concern due to kernel deadlock. No known exploits are reported in the wild, and no CVSS score has been assigned yet. The vulnerability was reserved in February 2024 and published in May 2024, indicating recent discovery and patching efforts.

For European organizations, the primary impact of CVE-2024-26987 is on system stability and availability rather than confidentiality or integrity. Systems running Linux kernels with hugetlb_optimize_vmemmap enabled and handling huge pages in environments that perform memory failure testing or CPU hotplug operations are at risk of experiencing kernel deadlocks. This can lead to system hangs, requiring reboots and causing downtime. Critical infrastructure, data centers, cloud providers, and enterprises relying on Linux servers for high-performance computing or memory-intensive applications may face operational disruptions. The deadlock could affect virtualized environments and containerized workloads where huge pages are used to optimize memory performance. Although no direct exploitation for privilege escalation or data theft is indicated, the denial-of-service-like effect can impact service availability, potentially violating SLAs and causing financial and reputational damage. Organizations with automated memory failure handling or CPU hotplugging in their Linux systems are particularly vulnerable. The lack of known exploits reduces immediate risk, but unpatched systems remain susceptible to stability issues.

1. Apply the official Linux kernel patch that fixes the deadlock condition as soon as it becomes available from trusted Linux distributions or the kernel mainline. 2. Temporarily disable the hugetlb_optimize_vmemmap feature if patching is not immediately feasible, to avoid triggering the deadlock scenario. 3. Review and audit kernel configurations and memory management settings related to huge pages and CPU hotplugging to ensure they align with best practices and do not enable unnecessary features that increase risk. 4. Implement robust monitoring of kernel logs and system health to detect early signs of deadlocks or hangs related to memory failure or CPU hotplug operations. 5. For virtualized or containerized environments, coordinate with hypervisor and container orchestration teams to manage huge page usage carefully and avoid configurations that might trigger this vulnerability. 6. Maintain updated backups and disaster recovery plans to minimize downtime impact if a deadlock occurs. 7. Engage with Linux vendor support channels for guidance on backported patches and kernel updates tailored to specific distributions used within the organization.