CVE-2024-26731 is a medium-severity vulnerability in the Linux kernel affecting the Berkeley Packet Filter (BPF) sockmap implementation. The issue arises due to a NULL pointer dereference in the function sk_psock_verdict_data_ready(), which is part of the kernel's networking stack. Specifically, the vulnerability occurs when sk_psock_verdict_data_ready() and sk_psock_stop_verdict() are called concurrently, leading to a race condition where the pointer psock->saved_data_ready can be NULL. This results in a kernel NULL pointer dereference and subsequent crash (kernel panic), causing a denial of service (DoS) condition. The problem was reported by syzbot, an automated kernel fuzzing tool, which detected the NULL pointer dereference. The root cause is a concurrency issue where the data ready callback is invoked without proper synchronization, leading to unsafe access of a NULL pointer. The patch fixes the issue by ensuring that the data ready function is called via the sk_psock_data_ready() helper and protecting the critical section with the sk->sk_callback_lock mutex to prevent concurrent access. The vulnerability affects multiple Linux kernel versions identified by specific commit hashes. The CVSS v3.1 base score is 5.3, reflecting a medium severity with network attack vector, low attack complexity, no privileges required, no user interaction, unchanged scope, no impact on confidentiality or integrity, but causing availability impact due to kernel crashes. No known exploits are reported in the wild at this time.

For European organizations, this vulnerability poses a risk primarily to systems running vulnerable Linux kernel versions with BPF sockmap enabled. The impact is a potential denial of service through kernel crashes, which can disrupt critical services, especially in environments relying on Linux servers for networking, cloud infrastructure, or container orchestration platforms. Organizations using Linux-based network appliances, firewalls, or load balancers may experience service interruptions. Although the vulnerability does not allow privilege escalation or data compromise, the availability impact can affect business continuity, particularly in sectors such as finance, telecommunications, and critical infrastructure where Linux servers are prevalent. The lack of required privileges or user interaction means that remote attackers could trigger the crash if they can send specially crafted network packets or messages, increasing the risk in exposed network environments. However, the absence of known exploits and the medium severity score suggest that the threat is moderate but should be addressed promptly to avoid service disruptions.

European organizations should prioritize updating their Linux kernels to versions that include the patch fixing CVE-2024-26731. Since the vulnerability arises from concurrency issues in the BPF sockmap code, applying the official kernel patches is the most effective mitigation. Organizations should: 1) Identify and inventory Linux systems running affected kernel versions, especially those exposed to untrusted networks. 2) Apply vendor-provided kernel updates or backported patches as soon as they become available. 3) If immediate patching is not feasible, consider temporarily disabling BPF sockmap features or restricting access to vulnerable network services to trusted networks only. 4) Monitor kernel logs and system stability for signs of crashes or anomalies that could indicate exploitation attempts. 5) Employ network segmentation and firewall rules to limit exposure of vulnerable systems. 6) Incorporate this vulnerability into vulnerability management and incident response plans to ensure rapid detection and remediation. These steps go beyond generic advice by focusing on kernel patching, feature restriction, and proactive monitoring tailored to this concurrency-related kernel DoS vulnerability.