CVE-2024-26810 is a medium severity vulnerability identified in the Linux kernel, specifically within the vfio/pci subsystem that handles PCI device virtualization and interrupt management. The vulnerability arises from a race condition involving the masking of external INTx interrupts through configuration space changes and concurrent ioctl operations that modify interrupt configurations. The core issue is that mask operations performed via config space changes to disable INTx (DisINTx) can race against interrupt configuration changes done through ioctl calls. This race condition occurs because the irq_type variable, which indicates the interrupt type, is updated while holding a lock called igate, but testing whether an interrupt is INTx (is_intx()) requires holding the same lock. Without proper synchronization, clearing the DisINTx flag from config space can conflict with simultaneous interrupt configuration changes, potentially leading to inconsistent or unexpected interrupt states. The fix involves introducing wrappers that add locking around paths outside the core interrupt code to serialize access and prevent race conditions. This synchronization ensures that interfaces triggering INTx eventfds are properly serialized, either by holding igate or by enabling them only when INTx is configured. A subsequent patch further enhances synchronization for related flows. The vulnerability does not affect confidentiality or integrity directly but impacts availability, as improper interrupt handling can cause system instability or denial of service. The CVSS v3.1 score is 4.4 (medium), reflecting that exploitation requires local access with high privileges (PR:H), no user interaction, and affects availability only. There are no known exploits in the wild at this time, and the affected versions correspond to specific Linux kernel commits prior to the patch date of April 5, 2024.

For European organizations, the impact of CVE-2024-26810 primarily concerns systems running Linux kernels with the vulnerable vfio/pci code, especially those utilizing PCI device virtualization or advanced interrupt configurations. Such systems are common in data centers, cloud providers, telecom infrastructure, and enterprises relying on Linux-based virtualization or containerization platforms. Exploitation could lead to denial of service conditions, causing system crashes or instability, which may disrupt critical services or workloads. While the vulnerability requires local high-privilege access, insider threats or compromised administrative accounts could leverage this flaw to degrade system availability. This is particularly relevant for sectors with stringent uptime requirements such as finance, healthcare, and industrial control systems prevalent in Europe. The lack of confidentiality or integrity impact reduces the risk of data breaches, but availability disruptions can still have significant operational and reputational consequences. Since the vulnerability affects kernel-level interrupt handling, recovery may require system reboots or kernel updates, impacting maintenance windows and operational continuity.

European organizations should prioritize applying the official Linux kernel patches that address this race condition in the vfio/pci subsystem as soon as they become available from their Linux distribution vendors. Given the complexity of the kernel code involved, relying on vendor-supplied updates ensures proper integration and testing. In the interim, organizations should restrict local administrative access to trusted personnel only and monitor for unusual kernel or interrupt-related errors that could indicate exploitation attempts. Implementing strict access controls and auditing on systems running vulnerable kernels can reduce the risk of exploitation. For environments using virtualization heavily, consider isolating critical workloads on hosts with updated kernels and limiting exposure of PCI device passthrough features where possible. Additionally, organizations should review their incident response plans to include scenarios involving kernel-level denial of service and ensure backup and recovery procedures are robust to minimize downtime. Regularly updating and patching Linux systems remains the most effective mitigation strategy.