CVE-2024-26772 is a medium severity vulnerability identified in the Linux kernel's ext4 filesystem implementation. Specifically, the flaw resides in the ext4_mb_find_by_goal() function, which is responsible for allocating blocks within the ext4 filesystem. The vulnerability arises because the logic that checks whether a block group’s block bitmap is corrupted was not properly protected by the group lock. This oversight could lead to the allocation of blocks from a corrupted block group bitmap. Such improper allocation can cause filesystem inconsistencies or corruption, potentially leading to denial of service conditions due to data loss or filesystem instability. The patch for this vulnerability places the bitmap corruption check under the protection of the group lock, ensuring that corrupted block groups are not used for block allocation. The vulnerability requires local privileges (low attack complexity and privileges required) but does not require user interaction. The CVSS v3.1 score is 5.5 (medium severity), reflecting that while confidentiality and integrity are not impacted, availability can be significantly affected. No known exploits are currently reported in the wild. The affected versions are specific Linux kernel commits prior to the fix, and the vulnerability was published on April 3, 2024.

For European organizations, this vulnerability poses a risk primarily to systems running Linux with ext4 filesystems, which is the default filesystem for many Linux distributions widely used in enterprise environments, cloud infrastructure, and embedded systems. The impact is mainly on availability, as exploitation could cause filesystem corruption leading to service outages, data loss, or system crashes. This can disrupt critical business operations, especially for organizations relying on Linux servers for web hosting, databases, or file storage. Since the vulnerability requires local access with some privileges, the threat is higher in environments where multiple users have shell access or where attackers can escalate privileges locally. The risk is elevated for organizations with large-scale Linux deployments, including cloud service providers, hosting companies, and enterprises using Linux-based infrastructure. While confidentiality and integrity are not directly impacted, the potential for denial of service can have cascading effects on operational continuity and compliance with data availability requirements under regulations like GDPR.

European organizations should promptly apply the official Linux kernel patches that address CVE-2024-26772. This involves updating to the fixed kernel versions provided by their Linux distribution vendors. For environments where immediate patching is not feasible, organizations should restrict local access to trusted users only and monitor for unusual filesystem errors or crashes that could indicate exploitation attempts. Implementing strict privilege separation and minimizing the number of users with write access to the filesystem can reduce risk. Regular filesystem integrity checks and backups should be maintained to enable recovery in case of corruption. Additionally, organizations should audit and harden their local access controls and consider deploying host-based intrusion detection systems to detect anomalous behavior related to filesystem operations. Coordination with Linux distribution security advisories and maintaining an up-to-date patch management process is critical to mitigate this vulnerability effectively.