CVE-2024-50283 is a high-severity vulnerability identified in the Linux kernel's implementation of the ksmbd (Kernel SMB Daemon) component, specifically within the handling of the SMB3 protocol pre-authentication hash response (smb3_preauth_hash_rsp). The vulnerability is classified as a use-after-free (CWE-416) flaw, which occurs when the kernel improperly manages memory related to user sessions during SMB3 pre-authentication. The root cause is that the function ksmbd_user_session_put, responsible for decrementing the reference count and potentially freeing the user session, was not called under the smb3_preauth_hash_rsp function. This omission could lead to the premature freeing of a session object before the pre-authentication hash response is fully processed, resulting in a use-after-free condition. Exploiting this flaw could allow an attacker with local privileges (as indicated by the CVSS vector AV:L/PR:L/UI:N) to execute arbitrary code or cause a denial of service by triggering memory corruption in the kernel. The vulnerability impacts confidentiality, integrity, and availability, as successful exploitation can lead to kernel-level code execution or system crashes. The vulnerability affects specific Linux kernel versions identified by commit hashes, and while no known exploits are currently reported in the wild, the high CVSS score of 7.8 reflects the significant risk posed by this flaw. The fix involves ensuring that ksmbd_user_session_put is properly called within smb3_preauth_hash_rsp to maintain correct session lifecycle management and prevent use-after-free errors.

For European organizations, this vulnerability poses a substantial risk, especially for those relying on Linux servers that utilize the ksmbd service for SMB3 file sharing and authentication. Exploitation could lead to unauthorized kernel-level code execution, allowing attackers to escalate privileges, access sensitive data, or disrupt critical services. This is particularly concerning for sectors such as finance, healthcare, government, and critical infrastructure, where Linux-based systems are prevalent and data confidentiality and system availability are paramount. The vulnerability's local attack vector means that attackers would need some level of access to the system, but once achieved, the impact could be severe, including full system compromise. Additionally, the SMB protocol is widely used for network file sharing, so environments with extensive SMB usage are at higher risk. The absence of known exploits currently provides a window for proactive patching and mitigation, but the high severity demands immediate attention to prevent potential exploitation.

European organizations should prioritize applying the official Linux kernel patches that address CVE-2024-50283 as soon as they become available. Until patches are deployed, organizations should: 1) Restrict local access to Linux systems running ksmbd by enforcing strict access controls and monitoring for unauthorized login attempts. 2) Limit the use of SMB3 services to only necessary systems and network segments, employing network segmentation and firewall rules to reduce exposure. 3) Implement enhanced logging and monitoring for unusual kernel or SMB-related activity that could indicate exploitation attempts. 4) Conduct thorough audits of Linux systems to identify and update any affected kernel versions, ensuring that all systems are running supported and patched releases. 5) Educate system administrators about the vulnerability and the importance of timely patch management. 6) Consider temporarily disabling ksmbd services on non-critical systems if immediate patching is not feasible, balancing operational needs with security risks.