CVE-2024-56561 is a high-severity vulnerability identified in the Linux kernel's PCI endpoint (EPC) subsystem. The flaw arises in the pci_epc_destroy() function, which is responsible for releasing PCI domain IDs when destroying PCI endpoint controllers. The vulnerability is a use-after-free condition caused by improper handling of device pointers during domain ID release. Specifically, pci_epc_destroy() calls pci_bus_release_domain_nr() passing 'epc->dev' as an argument; however, 'epc->dev' has already been freed by device_unregister(), leading to a use-after-free scenario (CWE-416). Additionally, the domain ID corresponds to the EPC device's parent, so passing 'epc->dev' is semantically incorrect. The fix involves passing 'epc->dev.parent' to pci_bus_release_domain_nr() and ensuring this call occurs before device_unregister(), preventing the use-after-free. This vulnerability can lead to memory corruption, potentially allowing attackers with low privileges (PR:L) and local access (AV:L) to escalate privileges or cause denial of service. The CVSS v3.1 score is 7.8, reflecting high impact on confidentiality, integrity, and availability without requiring user interaction. No known exploits are currently reported in the wild, but the vulnerability affects specific Linux kernel versions identified by their commit hashes.

For European organizations, this vulnerability poses a significant risk, especially those relying on Linux-based systems in critical infrastructure, data centers, and enterprise environments. The use-after-free flaw can be exploited by local attackers with limited privileges to execute arbitrary code with elevated privileges or cause system crashes, impacting system availability and data integrity. This is particularly concerning for sectors such as finance, healthcare, telecommunications, and government agencies where Linux servers are prevalent. The vulnerability could be leveraged to bypass security controls, access sensitive data, or disrupt services. Given the widespread use of Linux in European IT environments, unpatched systems could face increased risk of targeted attacks or lateral movement within networks. Although exploitation requires local access, insider threats or attackers who gain initial footholds could escalate privileges rapidly.

European organizations should prioritize patching affected Linux kernel versions as soon as vendor updates become available, ensuring the fix that passes 'epc->dev.parent' before device_unregister() is applied. System administrators should audit their environments to identify systems running vulnerable kernel versions using the provided commit hashes or vendor advisories. Employing strict access controls to limit local user privileges can reduce exploitation risk. Additionally, implementing kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR), Control Flow Integrity (CFI), and enabling security modules like SELinux or AppArmor can mitigate exploitation impact. Regularly monitoring system logs for anomalous behavior related to PCI device management and conducting vulnerability scans will help detect attempts to exploit this vulnerability. For environments where immediate patching is not feasible, consider isolating critical systems and restricting local access to trusted personnel only.