CVE-2024-35904 is a vulnerability identified in the Linux kernel related to the SELinux filesystem mount process. Specifically, the flaw occurs in the kernel function kern_mount(), which is responsible for mounting filesystems. When kern_mount() fails, it returns an error pointer. The vulnerability arises because the kernel code incorrectly continues execution and dereferences this error pointer instead of properly handling the error return path. This results in a use-after-free or dereference of invalid memory, which can lead to kernel crashes or potentially arbitrary code execution in kernel space. The issue is tied to the SELinux filesystem (selinuxfs) mount operation, where an unused static variable selinuxfs_mount was also removed as part of the fix. The vulnerability is rooted in improper error handling and pointer dereferencing in kernel code, which is a common source of critical kernel vulnerabilities. Although no known exploits are reported in the wild yet, the nature of the flaw—kernel memory corruption—makes it a serious concern. Attackers with the ability to trigger a mount operation could exploit this to cause denial of service or escalate privileges by executing code in kernel context. The vulnerability affects Linux kernel versions identified by the commit hash 0619f0f5e36f12e100ef294f5980cfe7c93ff23e, indicating it is present in recent kernel builds prior to the patch date of May 19, 2024. Since SELinux is widely used in many Linux distributions, this vulnerability has broad implications for systems relying on SELinux for mandatory access control. The fix involves correcting the error handling path to return the error pointer immediately upon failure, preventing any invalid dereference and improving kernel stability and security.

For European organizations, the impact of CVE-2024-35904 can be significant, especially for enterprises and government entities that rely heavily on Linux servers with SELinux enabled for security enforcement. Exploitation could lead to system crashes causing denial of service, disrupting critical services and operations. More critically, if exploited for privilege escalation, attackers could gain root-level access, compromising confidentiality, integrity, and availability of sensitive data and systems. This is particularly concerning for sectors such as finance, healthcare, telecommunications, and public administration, where Linux servers are prevalent and data protection regulations like GDPR impose strict security requirements. The vulnerability also poses risks to cloud service providers and hosting environments running Linux-based virtual machines or containers with SELinux enabled. Although no active exploits are known, the ease of triggering mount operations and the kernel-level impact mean that attackers with local access or the ability to induce mount failures could leverage this flaw. Therefore, timely patching is essential to prevent potential exploitation and maintain operational continuity and compliance with European cybersecurity standards.

1. Immediate application of the official Linux kernel patch that addresses CVE-2024-35904 is the primary mitigation step. Organizations should monitor their Linux distribution vendors for updated kernel packages and deploy them promptly. 2. For environments where immediate patching is not feasible, restrict access to systems to trusted users only, minimizing the risk of local exploitation. 3. Implement strict controls on mount operations, including limiting mount privileges to trusted administrators and using SELinux policies to restrict mount-related actions. 4. Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and Kernel Page Table Isolation (KPTI) to reduce the risk of exploitation. 5. Monitor system logs for unusual mount failures or kernel errors that could indicate attempted exploitation. 6. Conduct regular security audits and vulnerability scans focusing on kernel versions and SELinux configurations. 7. For cloud environments, coordinate with providers to ensure underlying host kernels are patched and that container runtimes enforce strict isolation. 8. Maintain an incident response plan to quickly address any suspected exploitation attempts involving kernel vulnerabilities.