CVE-2021-47374 is a vulnerability identified in the Linux kernel related to the dma-debug subsystem, which is responsible for debugging Direct Memory Access (DMA) operations. The issue arises when certain drivers that utilize the DMA API encounter an error condition that triggers an error message repeatedly, potentially millions of times per second. This excessive logging floods the kernel's printk buffer, leading to a significant increase in CPU usage, potentially up to 100%. This behavior can degrade system performance severely, causing resource exhaustion and potentially impacting system stability. The root cause is that the error message is not rate-limited, allowing it to overwhelm the system under specific conditions. The Linux kernel maintainers addressed this by changing the error handling to use err_printk() instead of simple rate limiting, aiming to make the issue more visible for other drivers that might suffer from similar problems. This fix helps identify and mitigate the problem more effectively. The vulnerability affects certain versions of the Linux kernel identified by specific commit hashes, and no known exploits are currently reported in the wild. While the vulnerability does not directly allow code execution or privilege escalation, the resulting resource exhaustion can lead to denial of service (DoS) conditions.

For European organizations, this vulnerability poses a risk primarily to systems running affected Linux kernel versions, especially those using drivers that interact with the DMA API. The impact includes potential denial of service due to CPU resource exhaustion, which can disrupt critical services, degrade performance, and increase operational costs. Organizations relying on Linux-based infrastructure for servers, embedded devices, or network equipment could experience service interruptions. This is particularly relevant for industries with high availability requirements such as telecommunications, finance, healthcare, and manufacturing. Additionally, the increased CPU load could mask other security monitoring activities or lead to system instability, indirectly affecting security posture. However, since exploitation requires triggering specific driver error conditions and no remote code execution or privilege escalation is involved, the threat is more about availability than confidentiality or integrity.

To mitigate this vulnerability, European organizations should: 1) Apply the latest Linux kernel patches that address CVE-2021-47374 as soon as they become available from their Linux distribution vendors or upstream kernel sources. 2) Identify and audit systems running affected kernel versions, especially those using hardware or drivers that rely on the DMA API. 3) Monitor kernel logs for unusual error message flooding related to dma-debug to detect potential triggering of this issue. 4) Implement resource monitoring and alerting to detect abnormal CPU usage spikes that could indicate exploitation attempts or system instability. 5) For embedded or specialized devices, coordinate with hardware vendors to ensure updated firmware or kernel versions are deployed. 6) Consider isolating critical systems or applying workload balancing to reduce the impact of potential CPU exhaustion. 7) Maintain robust backup and recovery procedures to minimize downtime in case of denial of service.