CVE-2021-47172 is a medium severity vulnerability in the Linux kernel's Industrial I/O (IIO) subsystem, specifically affecting the Analog-to-Digital Converter (ADC) driver for the AD7124 device. The root cause of the vulnerability is improper handling of channel numbering within the driver. The Linux kernel expects channel numbers to start at zero and be sequential without gaps. However, if channel numbers are non-sequential or have holes, this can lead to an integer overflow in the storage allocation or indexing logic. This overflow could cause memory corruption or out-of-bounds access within kernel space. The issue was introduced as part of a previous fix aimed at supporting arbitrary ordering of child nodes without relying on their order, but it failed to enforce the requirement that all channels must be present and sequential. The vulnerability was discovered during testing with QEMU, a hardware virtualization tool, indicating that it can be triggered in virtualized environments as well. Although the patch applied is considered minimal and primarily for backporting purposes, it addresses the overflow by enforcing the sequential channel numbering constraint. The vulnerability is classified under CWE-120 (Classic Buffer Overflow), and the CVSS v3.1 score is 5.5, reflecting a medium severity with local attack vector, low attack complexity, requiring low privileges, no user interaction, and impacting availability only. No known exploits are reported in the wild at this time.

For European organizations running Linux systems with the affected AD7124 ADC driver, this vulnerability could lead to denial-of-service conditions due to kernel crashes or instability caused by memory corruption. Since the vulnerability affects kernel-level code, exploitation could potentially disrupt critical services relying on Linux-based embedded systems, industrial control systems, or IoT devices that utilize the AD7124 ADC hardware. Although the impact on confidentiality and integrity is not indicated, availability degradation could affect operational continuity, especially in sectors like manufacturing, energy, or transportation where such hardware is common. The local attack vector and requirement for low privileges limit remote exploitation, but insider threats or compromised local accounts could leverage this vulnerability. The presence of this vulnerability in virtualized environments (QEMU) also suggests potential risks in cloud or testing infrastructures used by European enterprises. Given the widespread use of Linux across Europe in both enterprise and industrial contexts, the vulnerability poses a moderate risk that should be addressed promptly to maintain system reliability and availability.

European organizations should apply the official Linux kernel patches that address CVE-2021-47172 as soon as they become available for their specific kernel versions. For systems using long-term support (LTS) kernels or embedded Linux distributions, coordinate with vendors or maintainers to obtain backported fixes. In environments where patching is delayed, consider disabling or isolating the AD7124 ADC driver if it is not essential to operations. Conduct thorough inventory and asset management to identify devices and systems utilizing the affected driver. Implement strict access controls to limit local user privileges, reducing the risk of exploitation by low-privilege users. For virtualized environments, ensure that QEMU and related virtualization software are updated and monitored for anomalous behavior. Additionally, enhance kernel crash monitoring and logging to detect potential exploitation attempts early. Finally, integrate this vulnerability into vulnerability management and incident response workflows to ensure timely detection and remediation.