CVE-2024-35999 is a medium-severity vulnerability identified in the Linux kernel's SMB3 (Server Message Block version 3) implementation. The issue arises from a missing lock when accessing the session channel index, specifically a data race condition where the channel lock is not held during certain operations. This was detected by Coverity, a static analysis tool, which flagged the absence of proper synchronization leading to a potential race condition. In concurrent environments, such a missing lock can cause inconsistent or corrupted state within the SMB3 channel management, potentially leading to denial of service (DoS) conditions due to kernel instability or crashes. The vulnerability does not impact confidentiality or integrity directly, as it does not allow unauthorized data access or modification, but it affects availability by risking kernel crashes or hangs. The CVSS 3.1 score of 5.5 reflects this medium severity, with an attack vector of local (AV:L), requiring low privileges (PR:L), no user interaction (UI:N), and impacting availability (A:H) only. The vulnerability affects specific Linux kernel versions identified by commit hashes, indicating it is present in recent kernel builds prior to the patch. No known exploits are currently reported in the wild, but the presence of a race condition in a critical kernel subsystem like SMB3 warrants timely patching to prevent potential exploitation. This vulnerability is relevant for systems using SMB3 on Linux, commonly found in file servers, NAS devices, and enterprise environments relying on Linux-based SMB services.

For European organizations, the impact primarily concerns availability disruptions in Linux-based SMB3 file sharing services. Many enterprises, public sector institutions, and cloud providers in Europe utilize Linux servers for file sharing and storage solutions. An exploitation attempt or accidental triggering of this race condition could cause kernel panics or system crashes, leading to service outages and potential data access interruptions. This could affect business continuity, especially in sectors with high dependency on file sharing such as finance, manufacturing, healthcare, and government. Although no direct data breach risk is posed, the denial of service could indirectly impact operational integrity and availability of critical services. Additionally, organizations with strict uptime and compliance requirements (e.g., GDPR mandates on data availability and integrity) may face regulatory scrutiny if service disruptions occur. The lack of known exploits reduces immediate risk, but the vulnerability's presence in widely deployed Linux kernels means that unpatched systems remain exposed to potential future attacks or accidental failures.

To mitigate CVE-2024-35999, organizations should prioritize updating their Linux kernels to versions that include the patch fixing the missing lock in the SMB3 channel handling code. Since the vulnerability is local and requires low privileges, limiting access to systems running SMB3 services is critical. Implement strict access controls and ensure that only trusted users have local login or shell access to these servers. Employ kernel hardening techniques such as enabling kernel lockdown modes and using security modules like SELinux or AppArmor to restrict SMB3 service behavior. Monitoring system logs for kernel warnings or crashes related to SMB3 can provide early detection of exploitation attempts or instability. For environments using containerization or virtualization, ensure that underlying host kernels are patched, as containerized SMB3 services rely on host kernel stability. Finally, conduct regular vulnerability assessments and patch management cycles to maintain updated kernel versions and reduce exposure windows.