CVE-2021-46940 is a vulnerability identified in the Linux kernel, specifically related to the tools/power turbostat utility. The issue arises from an integer overflow in the index conversion functions idx_to_offset() and offset_to_idx(), which handle conversions between indices and offsets for Model-Specific Registers (MSRs) related to package energy statistics (MSR_PKG_ENERGY_STAT). The root cause is that idx_to_offset() returns a 32-bit signed integer (int), while MSR_PKG_ENERGY_STAT is an unsigned 32-bit integer (u32). This mismatch can cause the offset to be interpreted as a negative number when large values are processed, triggering a conditional check (if (offset < 0)) in the update_msr_sum() function. This check prevents the timer callback from updating the energy statistics in the background during long durations, effectively causing the turbostat tool to fail in accurately reporting energy consumption over extended periods. The vulnerability does not appear to directly compromise kernel security or system integrity but impacts the reliability and accuracy of power monitoring tools. The fix involves changing the return type from int to off_t (a signed type capable of representing file offsets) to correctly handle large offset values and prevent overflow. There are no known exploits in the wild, and the vulnerability primarily affects the turbostat tool's functionality rather than the core Linux kernel security. The affected versions correspond to specific Linux kernel commits identified by their hashes. No CVSS score has been assigned to this vulnerability yet.

For European organizations, the impact of CVE-2021-46940 is primarily operational rather than security-critical. Organizations relying on Linux-based systems for power management, energy monitoring, or performance tuning may experience inaccurate energy consumption data due to the turbostat tool failing to update statistics correctly over long durations. This could affect data center efficiency monitoring, energy cost optimization, and hardware performance analysis. While it does not directly lead to system compromise, inaccurate power metrics could indirectly impair decision-making related to energy usage and hardware maintenance. Industries with strict energy compliance requirements or those operating large-scale Linux server farms might find this issue more relevant. However, since no known exploits exist and the vulnerability does not allow privilege escalation or code execution, the confidentiality, integrity, and availability of systems remain largely unaffected.

To mitigate this vulnerability, European organizations should apply the patch provided by the Linux kernel maintainers that changes the idx_to_offset() and related functions to use the off_t type instead of int. Specifically, updating to the latest stable Linux kernel version that includes this fix is recommended. Organizations using turbostat for energy monitoring should verify that their tool version incorporates this patch. Additionally, system administrators should audit their monitoring and power management workflows to ensure that energy statistics are accurate and reliable. For environments where long-duration energy monitoring is critical, consider implementing supplementary monitoring tools or cross-validating turbostat data with hardware-level power metrics. Regularly updating Linux kernel and associated tools, and subscribing to Linux kernel security advisories, will help prevent similar issues. Since this vulnerability does not require user interaction or elevated privileges to manifest, ensuring up-to-date software is the primary defense.