CVE-2021-47498 is a medium-severity vulnerability in the Linux kernel related to the device mapper (DM) and block multi-queue (blk-mq) subsystem. The issue arises from improper handling of request queuing during the suspend phase of the device mapper. Specifically, the device mapper uses blk-mq's quiesce/unquiesce mechanism to stop and start the device mapper queue during suspend and resume operations. However, blk-mq's unquiesce function can be triggered by external events such as elevator switches or updates to the number of requests (nr_requests). This can cause requests to be queued during the suspend phase, which is unintended behavior. The vulnerability can lead to a kernel panic, particularly under stress conditions involving updates to nr_requests and dm-mpath suspend/resume cycles. The flaw was addressed by ensuring that requests are not queued to blk-mq during the DM suspend phase, preventing the kernel panic. The CVSS v3.1 score is 5.5 (medium), reflecting that the vulnerability requires local access with low privileges (PR:L), no user interaction (UI:N), and affects availability (A:H) but not confidentiality or integrity. There are no known exploits in the wild, and the vulnerability primarily impacts system stability rather than data confidentiality or integrity.

For European organizations, the primary impact of CVE-2021-47498 is on system availability and stability. Linux is widely used in enterprise servers, cloud infrastructure, and embedded systems across Europe. Systems utilizing device mapper multipath (dm-mpath) configurations, common in high-availability storage environments, are particularly at risk. A kernel panic triggered by this vulnerability could cause unexpected downtime, disrupting critical services and operations. This is especially significant for sectors relying on continuous uptime such as financial services, telecommunications, healthcare, and public administration. Although the vulnerability does not compromise confidentiality or integrity, the availability impact could lead to operational disruptions, potential data loss due to abrupt shutdowns, and increased maintenance costs. Since exploitation requires local access and low privileges, insider threats or compromised user accounts could trigger the issue. The absence of known exploits reduces immediate risk but does not eliminate the need for mitigation, especially in environments with frequent suspend/resume cycles or dynamic nr_requests updates.

To mitigate CVE-2021-47498, European organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from their Linux distribution vendors. 2) Review and harden access controls to limit local user privileges, reducing the risk of low-privilege users triggering the vulnerability. 3) Monitor systems using device mapper multipath configurations for unusual suspend/resume activity or kernel panics. 4) Implement system monitoring and alerting for kernel stability issues to enable rapid response. 5) Where possible, avoid or minimize suspend/resume operations on critical servers or storage nodes until patched. 6) Conduct thorough testing of kernel updates in staging environments that replicate production suspend/resume and nr_requests update scenarios to ensure stability before deployment. 7) Maintain robust backup and recovery procedures to mitigate potential data loss from unexpected system crashes.