CVE-2024-35813 is a vulnerability identified in the Linux kernel's MMC (MultiMediaCard) core subsystem. The issue arises from improper bounds checking in the code handling MMC requests, specifically in the commit identified as 4d0c8d0aef63. The vulnerable code assigns a value from an array using an index calculated as i - 1 without verifying that the iterator i is greater than zero. This leads to a potential negative index array access, which is undefined behavior in C and can cause memory corruption or access to unintended memory locations. The vulnerability is rooted in the failure to validate the iterator before accessing the array, which could lead to out-of-bounds reads or writes. The fix involves adding a check to ensure that the iterator i is greater than zero before performing the array access. This vulnerability affects multiple Linux kernel versions identified by specific commit hashes, indicating that it may be present in various kernel builds prior to the patch. Although no known exploits are currently reported in the wild, the nature of the vulnerability suggests that it could be leveraged by an attacker with local access to the system to cause a denial of service or potentially escalate privileges by corrupting kernel memory. The vulnerability does not require user interaction but does require the attacker to have the ability to trigger the affected MMC subsystem code path, which is typically accessible on systems using MMC storage devices or emulated MMC interfaces. The lack of a CVSS score means the severity must be assessed based on the technical details and potential impact.

For European organizations, the impact of CVE-2024-35813 depends largely on their use of Linux systems with MMC storage devices or emulated MMC interfaces. Many enterprise and industrial systems in Europe run Linux kernels that could be vulnerable if not updated. Exploitation could lead to system instability, crashes, or kernel memory corruption, potentially resulting in denial of service or privilege escalation. This could disrupt critical services, especially in sectors relying on embedded Linux devices, telecommunications infrastructure, or industrial control systems. The vulnerability could also be exploited in multi-tenant environments such as cloud or virtualized infrastructures where Linux is the host or guest OS, leading to cross-tenant attacks or escalation of privileges within the system. Given the widespread use of Linux in European IT infrastructure, failure to patch this vulnerability could expose organizations to targeted attacks or opportunistic exploitation by threat actors. The absence of known exploits suggests a window of opportunity for proactive mitigation before active exploitation occurs.

European organizations should prioritize updating their Linux kernels to versions that include the patch for CVE-2024-35813. Specifically, they should apply the commit 4d0c8d0aef63 or later kernel releases that incorporate this fix. For systems where immediate kernel updates are not feasible, organizations should audit and restrict access to MMC devices and interfaces, limiting the ability of unprivileged users to interact with the vulnerable subsystem. Employing kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR), Kernel Page Table Isolation (KPTI), and enabling security modules like SELinux or AppArmor can reduce the risk of exploitation. Monitoring system logs for unusual MMC subsystem activity and deploying intrusion detection systems capable of detecting anomalous kernel behavior can provide early warning of exploitation attempts. Additionally, organizations should review their supply chain and embedded device inventories to identify Linux-based devices that may require firmware or kernel updates. Coordinating with vendors to ensure timely patch deployment is critical. Finally, implementing strict access controls and segmentation for systems running vulnerable Linux kernels can limit the blast radius of a potential exploit.