CVE-2022-3586 is a use-after-free vulnerability identified in the Linux kernel's networking subsystem, specifically within the sch_sfb (Stochastic Fair Blue) queuing discipline implementation. The flaw arises from improper handling of the socket buffer (SKB) control buffer (cb) field after the SKB has been enqueued and subsequently freed in a child queuing discipline (qdisc). In this scenario, the sch_sfb enqueue function accesses the SKB cb field after the SKB memory has been released, leading to a use-after-free condition. This type of vulnerability can cause undefined behavior, including kernel crashes. Exploitation requires local access with at least low privileges, and no user interaction is necessary. The vulnerability does not impact confidentiality or integrity but results in a denial of service (DoS) by crashing the system. The issue was addressed and fixed in Linux kernel version 6.0. The CVSS v3.1 base score is 5.5 (medium severity), reflecting the local attack vector, low attack complexity, low privileges required, no user interaction, and impact limited to availability. No known exploits are reported in the wild as of the publication date. This vulnerability is classified under CWE-416 (Use After Free), a common memory corruption flaw that can lead to system instability or crashes if exploited.

For European organizations relying on Linux-based systems, particularly those using kernel versions prior to 6.0, this vulnerability poses a risk of local denial of service. Systems acting as network routers, firewalls, or servers that utilize the sch_sfb queuing discipline could be targeted by local users or attackers who have gained limited access, potentially causing system crashes and service interruptions. This could disrupt critical network services, impacting availability and operational continuity. While the vulnerability does not allow privilege escalation or data compromise, the induced downtime could affect business operations, especially in sectors with high availability requirements such as finance, telecommunications, and public infrastructure. Organizations with multi-tenant environments or shared hosting may face increased risk if unprivileged users can trigger the flaw. Given the local attack vector, remote exploitation is not feasible without prior access, limiting the threat scope but emphasizing the need for internal security controls and patch management.

To mitigate this vulnerability, European organizations should prioritize upgrading affected Linux systems to kernel version 6.0 or later, where the flaw is patched. For environments where immediate kernel upgrades are not feasible, consider disabling or avoiding the use of the sch_sfb queuing discipline to prevent triggering the vulnerable code path. Implement strict access controls to limit local user privileges and restrict unprivileged user access to network configuration or queuing disciplines. Employ kernel hardening techniques such as kernel lockdown modes and use security modules (e.g., SELinux, AppArmor) to reduce the attack surface. Regularly audit and monitor system logs for unusual kernel errors or crashes that may indicate exploitation attempts. Additionally, maintain robust patch management processes to ensure timely application of security updates. Network segmentation can also help isolate critical systems from untrusted users who might exploit this vulnerability.