CVE-2021-46941 is a vulnerability in the Linux kernel's USB driver, specifically within the DesignWare Core USB3 (dwc3) controller core driver. The issue arises from an incomplete implementation of the mode switching procedure for the Dual-Role Device (DRD) controller. According to the official programming guide for the dwc3 controller, switching between device and host modes requires a sequence of steps involving resetting the controller and setting specific registers. The vulnerability stems from missing critical steps: the core soft reset (GCTL.CoreSoftReset) is not performed when switching modes, and the device soft reset (DCTL.CSftRst) is incorrectly applied or omitted when switching from host to device mode. This improper handling can cause the USB controller to lock up or become unresponsive, as observed on platforms such as HiKey960 and Ferry's testing platform. The fix involves applying the missing core soft reset step and ensuring proper synchronization of clocks before clearing the reset, as well as applying the device soft reset only when switching from host to device mode. Although this vulnerability does not appear to be exploitable for remote code execution or privilege escalation, it can cause denial of service (DoS) conditions by locking the USB controller, thereby disrupting USB connectivity and potentially affecting devices relying on USB communications. No known exploits are reported in the wild, and the vulnerability primarily impacts systems running affected versions of the Linux kernel with the dwc3 USB controller driver in use.

For European organizations, the impact of CVE-2021-46941 is primarily related to availability disruptions in systems that utilize the affected Linux kernel versions with the dwc3 USB controller. This includes embedded systems, development boards, and potentially some server or workstation environments that rely on USB connectivity for critical peripherals or data transfer. Disruption of USB functionality can lead to operational downtime, loss of productivity, and complications in environments where USB devices are essential for daily operations, such as manufacturing, healthcare, or research institutions. While the vulnerability does not directly compromise confidentiality or integrity, the denial of service effect could indirectly impact business continuity and operational reliability. Organizations using hardware platforms like HiKey960 or similar ARM-based development boards common in IoT or edge computing deployments may be more susceptible. The absence of known exploits reduces immediate risk, but unpatched systems remain vulnerable to accidental lockups or targeted DoS attempts by local attackers or malicious insiders.

To mitigate CVE-2021-46941, European organizations should: 1) Ensure that all Linux systems using the dwc3 USB controller driver are updated to the latest kernel versions containing the patch that implements the correct mode switching sequence, including the core soft reset and device soft reset steps. 2) For embedded or specialized hardware platforms such as HiKey960, verify firmware and kernel updates from vendors that address this issue. 3) Implement monitoring for USB controller lockups or unusual USB device behavior to detect potential exploitation or accidental triggering of the vulnerability. 4) In environments where USB availability is critical, consider redundant USB interfaces or failover mechanisms to maintain operational continuity. 5) Restrict local access to systems with affected kernels to trusted personnel only, as exploitation requires local interaction. 6) Engage with hardware and software vendors to confirm that their products are not affected or have received appropriate patches. These steps go beyond generic patching advice by emphasizing hardware-specific updates, monitoring, and operational continuity planning.