CVE-2021-47293 is a vulnerability identified in the Linux kernel's network scheduling subsystem, specifically within the act_skbmod module. The vulnerability arises because the function tcf_skbmod_act() incorrectly assumes that all packets it processes use Ethernet as their Layer 2 (L2) protocol. However, this assumption is invalid for certain network device types such as CAN (Controller Area Network) devices, which use different L2 protocols. When skbmod actions like 'swap mac' are applied to non-Ethernet packets, such as those on virtual CAN devices (vcan0), the packets become silently corrupted. This occurs because the skbmod module attempts to modify Ethernet-specific header fields that do not exist or are structured differently in non-Ethernet packets, leading to data corruption and potential disruption of network communication. The vulnerability was addressed by updating the kernel to skip skbmod actions on non-Ethernet packets, preventing unintended packet corruption. This flaw does not appear to enable direct remote code execution or privilege escalation but can cause network reliability issues or data integrity problems in environments utilizing non-Ethernet network interfaces.

For European organizations, the impact of CVE-2021-47293 primarily concerns environments using Linux systems with network configurations involving non-Ethernet interfaces, such as CAN devices commonly found in automotive, industrial control, and embedded systems sectors. Packet corruption caused by this vulnerability can lead to network communication failures, degraded service availability, and potential data loss or misrouting in critical control networks. Organizations relying on Linux-based infrastructure for industrial automation, automotive telematics, or IoT deployments may experience operational disruptions. While this vulnerability does not directly compromise confidentiality or enable remote exploitation, the integrity and availability of network traffic in affected systems can be compromised, potentially impacting safety-critical applications and real-time control systems prevalent in European manufacturing and automotive industries.

To mitigate this vulnerability, organizations should ensure that their Linux kernel versions are updated to include the patch that prevents skbmod actions on non-Ethernet packets. Specifically, system administrators should: 1) Identify Linux systems using non-Ethernet network interfaces such as CAN or virtual CAN devices; 2) Apply the latest kernel updates from trusted Linux distributions that address CVE-2021-47293; 3) Review and audit traffic control (tc) configurations to avoid applying skbmod actions indiscriminately on all interfaces without protocol checks; 4) Implement monitoring to detect unusual packet corruption or network errors on affected interfaces; 5) For embedded or specialized devices where kernel updates are delayed, consider disabling skbmod actions on non-Ethernet interfaces as a temporary workaround; 6) Engage with device vendors to ensure timely firmware or kernel patches are applied in industrial or automotive environments. These steps go beyond generic patching by focusing on protocol-aware configuration and targeted monitoring in environments where non-Ethernet protocols are in use.