CVE-2021-47399 is a vulnerability in the Linux kernel's ixgbe network driver, which is responsible for managing Intel 10 Gigabit Ethernet network interfaces. The issue arises from improper handling of queue numbers related to XDP (eXpress Data Path) setup in systems with fewer than 63 online CPUs. Specifically, the vulnerability is triggered when a user sets the number of queues to 63 via the ethtool utility, exceeding the actual number of online CPUs (num_online_cpus). The ixgbe driver maintains several queue counts: num_rx_queues, num_tx_queues, and num_xdp_queues. Due to a logic flaw, num_rx_queues can be set higher than num_xdp_queues, leading to a NULL pointer dereference during the execution of the ixgbe_xdp_setup function. This dereference occurs when the driver attempts to access xdp_ring elements beyond the allocated range, resulting in a kernel panic and system crash. The vulnerability is rooted in the incorrect calculation and validation of queue limits, specifically in the functions ixgbe_set_channels and ixgbe_set_rss_queues, where the ring_feature limit is set to 63 without proper bounds checking against the number of online CPUs. The fix involves adjusting ixgbe_max_channels to ensure the number of queues cannot exceed num_online_cpus and modifying ixgbe_xdp_setup to use the smaller value between num_rx_queues and num_xdp_queues, preventing out-of-bounds access. This vulnerability does not require user interaction beyond setting queue parameters via ethtool and can be triggered locally by users with sufficient privileges to configure network interfaces. No known exploits are currently reported in the wild, and the vulnerability affects Linux kernel versions containing the ixgbe driver prior to the patch date.

For European organizations, this vulnerability poses a risk primarily to servers and network infrastructure running Linux with Intel 10 Gigabit Ethernet adapters using the ixgbe driver. The impact includes potential denial of service (DoS) due to kernel panics, leading to system crashes and network outages. This can disrupt critical services, especially in data centers, cloud providers, telecommunications, and enterprises relying on high-performance networking. Confidentiality and integrity are less directly impacted since the flaw causes crashes rather than unauthorized data access or modification. However, availability degradation can have cascading effects on business operations, service level agreements, and regulatory compliance, particularly in sectors like finance, healthcare, and public administration. The vulnerability requires local administrative privileges to exploit, limiting remote attack vectors but increasing risk from insider threats or compromised accounts. Given the widespread use of Linux in European IT infrastructure and the prevalence of Intel network hardware, the vulnerability could affect a broad range of organizations if unpatched. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits once the vulnerability is publicly disclosed.

European organizations should promptly apply the official Linux kernel patches that address CVE-2021-47399. Specifically, update the kernel to versions where ixgbe_max_channels is corrected to limit queue settings to the number of online CPUs and ixgbe_xdp_setup properly bounds queue usage. Network administrators should audit and restrict the use of ethtool commands that modify queue parameters, limiting such operations to trusted administrators only. Implement monitoring for kernel panics and unusual network interface configurations to detect potential exploitation attempts. For environments where immediate patching is not feasible, consider disabling XDP features on affected interfaces as a temporary workaround to prevent triggering the vulnerability. Additionally, review and enforce strict access controls on systems with Intel 10GbE adapters to prevent unauthorized local configuration changes. Regularly update and test incident response plans to handle potential DoS events caused by this or similar vulnerabilities. Finally, maintain awareness of vendor advisories and Linux kernel updates to ensure timely application of security fixes.