CVE-2024-50086 is a high-severity vulnerability identified in the Linux kernel's implementation of the SMB (Server Message Block) protocol server daemon, specifically within the ksmbd module. The vulnerability arises from a race condition between SMB2 session log off and session setup operations. This race condition can lead to a use-after-free (CWE-416) scenario where the session structure is freed while still in use, potentially allowing an attacker to execute arbitrary code, cause denial of service, or escalate privileges. The root cause is the lack of proper synchronization when marking a session as expired and managing the reference count of the session structure. The fix involves introducing a session_lock to serialize access when setting the SMB2_SESSION_EXPIRED flag and ensuring the session structure is not freed prematurely by correctly managing its reference count. The vulnerability requires local access with low privileges (PR:L) and no user interaction (UI:N), but the attack vector is local (AV:L), meaning an attacker must have some level of access to the system to exploit it. The CVSS v3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability. No known exploits are currently reported in the wild, but the nature of the vulnerability and its presence in the widely used Linux kernel SMB server component make it a significant risk if left unpatched.

For European organizations, this vulnerability poses a substantial risk, especially for enterprises relying on Linux servers for file sharing and SMB services. Exploitation could lead to unauthorized access to sensitive data, disruption of file sharing services, and potential lateral movement within networks. Given the high confidentiality, integrity, and availability impact, critical infrastructure, financial institutions, and government agencies using Linux-based SMB servers could face data breaches, operational downtime, and compliance violations under GDPR. The local attack vector means that insider threats or attackers who have gained limited access could leverage this vulnerability to escalate privileges or disrupt services. The absence of known exploits currently provides a window for proactive patching, but the vulnerability's severity necessitates urgent remediation to prevent exploitation in targeted attacks or by advanced persistent threat (APT) actors.

European organizations should immediately apply the latest Linux kernel patches that address CVE-2024-50086. Beyond patching, organizations should: 1) Restrict local access to SMB services by enforcing strict access controls and minimizing the number of users with local login privileges on Linux servers running ksmbd. 2) Implement robust monitoring and logging of SMB session activities to detect unusual session log off and setup patterns that may indicate exploitation attempts. 3) Employ kernel hardening techniques such as enabling kernel lockdown modes and using security modules like SELinux or AppArmor to limit the impact of potential exploitation. 4) Conduct regular vulnerability assessments and penetration testing focusing on SMB services to identify and remediate weaknesses proactively. 5) Segment networks to isolate SMB servers from less trusted network zones, reducing the risk of lateral movement. 6) Educate system administrators on the importance of timely patching and monitoring of SMB-related services.