CVE-2024-56675 is a high-severity use-after-free (UAF) vulnerability in the Linux kernel's Berkeley Packet Filter (BPF) subsystem, specifically related to the handling of BPF programs attached to uprobes. Uprobes are a Linux kernel feature that allows dynamic tracing of user-space applications by attaching BPF programs to user-space probes. The vulnerability arises from a mismatch in the Read-Copy-Update (RCU) grace period flavors used when detaching BPF programs from uprobes. Typically, uprobes use the tasks-trace-RCU flavor for synchronization, but non-sleepable BPF programs are freed using the normal RCU grace period. Since a normal RCU grace period does not guarantee the completion of a tasks-trace-RCU grace period, this discrepancy can lead to a use-after-free condition on the bpf_prog structure. This means that after detaching a BPF program, the kernel might still access freed memory, potentially leading to memory corruption, kernel crashes, or escalation of privileges. The fix involves explicitly waiting for a tasks-trace-RCU grace period after removing the attachment of a bpf_prog to a perf_event, ensuring proper synchronization and preventing premature freeing of the BPF program. The vulnerability is tracked under CWE-416 (Use After Free) and has a CVSS 3.1 base score of 7.8, indicating high severity. Exploitation requires local privileges with low complexity and no user interaction, and it impacts confidentiality, integrity, and availability of the affected systems. No known exploits are currently reported in the wild, but the nature of the vulnerability makes it a significant risk for systems running vulnerable Linux kernel versions.

For European organizations, this vulnerability poses a substantial risk, especially for those relying on Linux-based infrastructure, including servers, cloud environments, and embedded systems. Exploitation could allow an attacker with limited local privileges to execute arbitrary code in kernel space, potentially leading to full system compromise. This can result in unauthorized data access, disruption of critical services, and persistent backdoors. Given the widespread use of Linux in European public sector institutions, financial services, telecommunications, and manufacturing, the impact could be severe. Additionally, organizations using performance monitoring and tracing tools that leverage uprobes and BPF programs are particularly at risk. The vulnerability could be leveraged to bypass security controls, escalate privileges, or cause denial of service, affecting confidentiality, integrity, and availability of critical systems. The absence of known exploits currently provides a window for proactive mitigation, but the high severity score and ease of exploitation underline the urgency for patching.

European organizations should prioritize updating their Linux kernel to versions that include the fix for CVE-2024-56675. Since the vulnerability involves kernel-level components, applying vendor-provided kernel patches or upgrading to the latest stable kernel releases is essential. Organizations should audit their use of BPF programs and uprobes, especially in performance monitoring and tracing contexts, to identify potentially vulnerable configurations. Limiting local user privileges and enforcing strict access controls can reduce the risk of exploitation. Employing kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR), Control Flow Integrity (CFI), and seccomp filters can provide additional layers of defense. Monitoring kernel logs and system behavior for anomalies related to BPF program attachments or crashes may help detect exploitation attempts. Finally, organizations should maintain an up-to-date inventory of Linux kernel versions in use across their infrastructure to ensure timely patch management.