CVE-2021-47400 is a medium-severity vulnerability in the Linux kernel's hns3 network driver, specifically related to the function hns3_nic_net_open(). The vulnerability arises because the function hns3_nic_net_open() can be called repeatedly without proper checks, which is not the intended behavior. This occurs during concurrent device reset and traffic control (tc) setup operations, creating a race condition that allows hns3_nic_net_open() to be invoked multiple times. The root cause is the lack of verification of the HNS3_NIC_STATE_DOWN flag before executing the function, leading to a kernel bug triggered by calling napi_enable() twice. The kernel bug manifests as a kernel panic or BUG error, causing the affected system to crash or become unstable. The call trace provided shows the kernel panic occurs at net/core/dev.c:6991, with the stack trace involving the hns3 and hclge modules. This vulnerability affects Linux kernel versions containing the hns3 driver, which is used for certain network interface cards (NICs), particularly those from Huawei's HiSilicon. The vulnerability does not impact confidentiality or integrity but affects availability by causing kernel crashes. Exploitation requires local access with the ability to trigger device reset and tc setup concurrently, and no user interaction or privileges beyond local access are needed. No known exploits are reported in the wild, and a patch involves adding a check for the HNS3_NIC_STATE_DOWN flag to prevent repeated calls to hns3_nic_net_open(). The CVSS v3.1 score is 4.0, reflecting low complexity but limited impact scope.

For European organizations, the primary impact of CVE-2021-47400 is on system availability and stability. Organizations using Linux servers or network devices with the hns3 driver, especially those employing Huawei HiSilicon NICs, may experience unexpected kernel panics leading to service disruptions. This can affect critical infrastructure, data centers, and cloud providers relying on these network interfaces. Although the vulnerability does not expose data confidentiality or integrity, repeated crashes can cause downtime, impacting business continuity and operational reliability. In sectors such as telecommunications, finance, and government, where high availability is crucial, this vulnerability could lead to significant operational challenges. Additionally, the need for local access to trigger the vulnerability limits remote exploitation risk but does not eliminate insider threat or attacker lateral movement scenarios. The absence of known exploits in the wild reduces immediate risk but patching is recommended to prevent potential future exploitation and maintain system stability.

1. Apply the official Linux kernel patches that address CVE-2021-47400 as soon as they become available from trusted sources or Linux distributions. 2. For systems using Huawei HiSilicon NICs with the hns3 driver, verify the driver version and update to a patched kernel version. 3. Implement strict access controls to limit local user privileges and prevent unauthorized users from triggering device resets or tc setups. 4. Monitor kernel logs for signs of repeated hns3_nic_net_open() calls or kernel BUG messages related to net/core/dev.c to detect potential exploitation attempts or instability. 5. In virtualized or containerized environments, isolate network device management to reduce the risk of concurrent operations triggering the vulnerability. 6. Coordinate with hardware vendors and Linux distribution maintainers to ensure timely updates and compatibility testing. 7. Consider temporary workarounds such as disabling or unloading the hns3 driver if feasible and if network functionality is not critical, until patches are applied.