CVE-2024-31076 is a vulnerability identified in the Linux kernel related to the handling of interrupt vectors during CPU hotplug operations, specifically within the genirq/cpuhotplug and x86/vector subsystems. The issue arises from the improper reclamation of interrupt vectors when an interrupt's affinity is reconfigured to a different CPU, and the original CPU is taken offline before the interrupt triggers on the new CPU. Normally, when interrupt affinity changes, the kernel defers the vector reclamation until the interrupt triggers on the new CPU, at which point the old vector is reclaimed via a cleanup process. However, if the original CPU goes offline before this trigger, the cleanup routine is not properly invoked, leaving the old interrupt vector unreclaimed in the vector matrix. This results in a CPU vector leak, which can degrade system stability and resource availability over time. The patch involves reordering the invocation of irq_force_complete_move() to ensure vectors are reclaimed if the interrupt was previously affine to the outgoing CPU, and adding additional reclamation logic in the vector cleanup function to handle edge cases where the CPU is offline. This vulnerability affects specific Linux kernel versions identified by the commit hash f0383c24b4855f6a4b5a358c7b2d2c16e0437e9b and was published on June 21, 2024. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet.

For European organizations, this vulnerability poses a risk primarily to systems running affected Linux kernel versions, especially those utilizing CPU hotplug features common in high-availability servers, cloud infrastructure, and virtualized environments. The CPU vector leak can lead to resource exhaustion in the interrupt vector matrix, potentially causing degraded system performance, increased latency in interrupt handling, and in worst cases, system instability or crashes. This can impact critical infrastructure, data centers, and enterprise environments relying on Linux for their operations. While the vulnerability does not directly lead to privilege escalation or remote code execution, the resulting instability could be exploited indirectly by attackers to cause denial of service or disrupt services. Given the widespread use of Linux in European IT environments, particularly in sectors such as finance, telecommunications, and government, the impact could be significant if left unpatched. The absence of known exploits suggests the threat is currently low but could increase as awareness grows.

European organizations should prioritize updating their Linux kernel to the patched versions that address CVE-2024-31076. Specifically, system administrators should: 1) Identify all systems running affected kernel versions using the commit hash or kernel version mapping; 2) Apply vendor-provided kernel updates or patches that include the fix for this vulnerability; 3) For environments using CPU hotplug features extensively, conduct thorough testing post-patch to ensure stability; 4) Monitor system logs for unusual interrupt handling behavior or vector leak warnings; 5) Implement proactive resource monitoring to detect early signs of vector exhaustion; 6) Where kernel updates are delayed, consider temporarily disabling CPU hotplug features if feasible to reduce exposure; 7) Engage with Linux distribution vendors for timely security advisories and patches; 8) Incorporate this vulnerability into vulnerability management and incident response plans to ensure rapid remediation upon detection.