CVE-2021-47562 is a vulnerability identified in the Linux kernel related to the handling of transmit queue mapping (txq_map) sizing in the ice network driver, which supports Intel Ethernet devices. The root cause stems from a mismatch in assumptions about the number of transmit (Tx) and receive (Rx) queues when using eXpress Data Path (XDP) rings configured per CPU. Specifically, the vulnerability arises because the vsi->txq_map array size was incorrectly set to twice the vsi->alloc_txq value, without accounting for the actual number of possible CPUs (num_possible_cpus()). This discrepancy leads to out-of-bounds access and a NULL pointer dereference in kernel space when the Rx queue count differs from the Tx queue count, causing a kernel crash (kernel oops). The vulnerability manifests during operations such as changing ethtool channel settings or configuring XDP rings, as evidenced by kernel logs showing a NULL pointer dereference and stack trace involving ice_vsi_rebuild and related functions. The fix involves adjusting the sizing logic to consider both the number of allocated Tx queues and the number of possible CPUs, preventing the out-of-bounds access. This vulnerability is a logic error in the network driver that can be triggered by local users with privileges to reconfigure network interfaces, leading to denial of service (DoS) via kernel crash. There is no indication of remote exploitation or privilege escalation, and no known exploits in the wild have been reported as of the publication date. The vulnerability affects Linux kernel versions containing the affected ice driver code prior to the patch date, with the specific commit hashes referenced. The issue is technical and requires kernel-level patching to remediate.

For European organizations, the primary impact of CVE-2021-47562 is the potential for local denial of service on Linux systems running affected Intel Ethernet hardware with the ice driver. This can disrupt network connectivity and availability of critical services, especially in data centers, cloud environments, and enterprise networks where Linux servers are prevalent. Organizations relying on high-performance networking with XDP or ethtool channel configurations may experience instability or crashes if the vulnerability is triggered. While the vulnerability does not directly lead to data breaches or privilege escalation, the resulting kernel crashes can cause service interruptions, impacting business continuity and operational efficiency. In sectors such as finance, telecommunications, healthcare, and government, where Linux servers are widely deployed, such disruptions could have significant operational and reputational consequences. Additionally, the need to apply kernel patches and reboot systems to remediate the issue may require planned maintenance windows, affecting service availability. Since the vulnerability requires local access and privileged operations to exploit, the risk is mitigated by strong access controls; however, insider threats or compromised accounts could leverage this flaw to cause denial of service.

To mitigate CVE-2021-47562, European organizations should: 1) Identify Linux systems using Intel Ethernet devices supported by the ice driver, particularly those running kernel versions prior to the patch date. 2) Apply the official Linux kernel patches that fix the txq_map sizing logic as soon as they become available from trusted sources or Linux distribution vendors. 3) If immediate patching is not feasible, restrict access to privileged users who can modify network interface settings or use ethtool to prevent triggering the vulnerability. 4) Monitor system logs for kernel oops or crashes related to the ice driver and ethtool operations to detect potential exploitation attempts or instability. 5) Test kernel updates in staging environments to ensure compatibility with existing network configurations, especially those using XDP or advanced channel settings. 6) Maintain strict user privilege management and audit network configuration changes to reduce the risk of accidental or malicious triggering of the vulnerability. 7) Consider network segmentation and isolation of critical Linux servers to limit exposure to local attackers. These steps go beyond generic advice by focusing on hardware-specific driver patching, access control to network configuration tools, and proactive monitoring of kernel stability.