CVE-2021-47577 is a vulnerability identified in the Linux kernel's IO workqueue (io-wq) subsystem. The issue arises from a race condition during the creation and cancellation of worker tasks when the workqueue is in the process of exiting. Specifically, the kernel checks the IO_WQ_BIT_EXIT flag before creating a new worker task_work to ensure the workqueue is not exiting. However, due to a timing gap, it is possible that the exit process cancels pending work after the check but before the new task_work is fully added, leading to a scenario where task_work is added after cancellation has begun. This race condition can cause inconsistencies in task management, potentially leading to use-after-free conditions or other memory corruption issues. The fix involves an additional check of the EXIT bit immediately after adding the creation task_work; if the EXIT bit is set, the same cancellation routine is executed to prevent the race condition. This vulnerability affects specific Linux kernel versions identified by commit hashes, indicating it is present in certain recent kernel builds prior to the patch. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2021-47577 depends on their reliance on vulnerable Linux kernel versions, particularly in environments where IO workqueues are heavily utilized, such as high-performance computing, servers, and embedded systems. Exploitation of this race condition could lead to kernel memory corruption, potentially allowing local attackers to escalate privileges or cause denial of service by crashing the kernel. This can compromise system integrity and availability, critical for sectors like finance, healthcare, and critical infrastructure. Although remote exploitation is unlikely without local access, the widespread use of Linux in European data centers, cloud providers, and enterprise environments means that vulnerable systems could be targeted by insiders or malware that gains initial foothold. The absence of known exploits reduces immediate risk, but the vulnerability's nature warrants prompt attention to prevent future exploitation attempts.

European organizations should prioritize updating Linux kernels to versions that include the patch for CVE-2021-47577. Specifically, kernel maintainers and system administrators must apply the fix that adds the post-addition EXIT bit check and cancellation logic. For environments where immediate patching is not feasible, mitigating risk involves restricting local access to trusted users only, employing strict privilege separation, and monitoring for unusual kernel crashes or system instability indicative of exploitation attempts. Additionally, organizations should audit their Linux kernel versions across all systems, including embedded devices and containers, to identify vulnerable instances. Implementing kernel live patching solutions where available can reduce downtime during remediation. Finally, maintaining robust endpoint detection and response (EDR) capabilities can help detect exploitation attempts targeting kernel vulnerabilities.