CVE-2021-46993 is a vulnerability identified in the Linux kernel's util-clamp (utilization clamping) subsystem, specifically within the scheduler component. Util-clamp is responsible for categorizing tasks into different buckets based on their clamp values to optimize performance. The vulnerability arises from an off-by-one error in the calculation of bucket sizes. The bucket size is computed using a rounding division, which can cause an incorrect bucket index to be assigned to a task. For example, with 20 buckets, the bucket size is calculated as 1024/20 = 51. A task with a clamp value of 1024 would be mapped to bucket ID 1024/51 = 20. However, valid bucket indices range from 0 to 19, so an index of 20 results in an out-of-bounds memory access. This out-of-bounds access can potentially lead to undefined behavior, including memory corruption or kernel crashes. The fix involves clamping the bucket ID to ensure it stays within the valid range, preventing the out-of-bound access. The vulnerability affects certain versions of the Linux kernel as indicated by the provided commit hashes, and it was publicly disclosed on February 28, 2024. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2021-46993 depends largely on their use of Linux-based systems, particularly those running kernels with the vulnerable util-clamp implementation. The vulnerability can lead to kernel instability or crashes due to out-of-bound memory access, potentially causing denial of service (DoS) conditions. In environments where Linux servers or embedded devices handle critical workloads, such instability could disrupt business operations, affecting availability and reliability. Although no known exploits exist currently, the vulnerability could be leveraged by attackers with local access or through crafted workloads to induce kernel crashes or potentially escalate privileges if combined with other vulnerabilities. This risk is particularly relevant for data centers, cloud providers, and enterprises relying on Linux for infrastructure services. Confidentiality and integrity impacts are less direct but cannot be fully ruled out if memory corruption leads to unpredictable kernel behavior. Given the widespread use of Linux across European industries, including finance, manufacturing, and government, the vulnerability poses a tangible risk to operational continuity and system security.

European organizations should prioritize updating their Linux kernel to the patched versions that address CVE-2021-46993. Since the vulnerability stems from a kernel-level bug, applying official kernel patches or upgrading to a fixed kernel release is the most effective mitigation. For environments where immediate patching is not feasible, organizations should restrict untrusted user access to systems running vulnerable kernels to reduce the risk of exploitation. Monitoring kernel logs for unusual scheduler or memory errors may help detect attempts to trigger the vulnerability. Additionally, implementing kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR), and enabling security modules like SELinux or AppArmor can provide layered defense. Organizations using containerized or virtualized Linux environments should ensure host kernels are patched, as guest workloads may attempt to exploit the vulnerability. Finally, maintaining an up-to-date inventory of Linux kernel versions deployed across the organization will facilitate timely remediation.