CVE-2025-21663 is a vulnerability in the Linux kernel's network driver subsystem, specifically affecting the stmmac driver for Nvidia Tegra MGBE Ethernet controllers. The issue arises because the driver is hardcoded to use the Stream ID (SID) of the MGBE0 controller for all Ethernet controllers, rather than reading the correct SID from the device tree for each controller. Nvidia's Tegra MGBE controllers require the IOMMU Stream ID to be written to the MGBE_WRAP_AXI_ASID0_CTRL register to function correctly. When the driver uses the incorrect SID for controllers other than MGBE0, it causes softirq timeouts and kernel panics. This manifests as network interface resets, transmit queue timeouts, and ultimately system instability or crashes. The vulnerability affects systems running Linux kernel versions that include this flawed driver implementation, particularly on Nvidia Tegra platforms such as the Orin AGX/Jetson family. The provided kernel logs demonstrate the problem occurring when an Ethernet cable is connected to the MGBE1 interface, leading to repeated resets and RCU (Read-Copy-Update) stalls, which indicate severe kernel-level performance degradation and potential deadlocks. Although no known exploits are currently reported in the wild, the vulnerability can cause denial of service (DoS) conditions due to kernel panics and network outages. The root cause is a driver logic flaw rather than a memory corruption or privilege escalation issue, limiting the scope to availability impacts. The vulnerability requires the affected hardware (Nvidia Tegra MGBE controllers) and the vulnerable Linux kernel driver, but no user interaction or authentication is needed to trigger the issue once the device is connected and active. No CVSS score has been assigned yet, but the technical details and logs confirm a serious stability problem that can disrupt network connectivity and system operation.

For European organizations using Nvidia Tegra-based embedded systems or edge devices running Linux kernels with the vulnerable stmmac driver, this vulnerability can cause significant operational disruptions. Industries relying on embedded Linux platforms for industrial automation, automotive systems, telecommunications infrastructure, or IoT deployments may experience network interface failures and kernel panics, leading to device reboots or downtime. This can impact critical services, especially in sectors like manufacturing, smart city infrastructure, and transportation where Nvidia Tegra platforms are deployed. The denial of service caused by kernel panics can interrupt data flows, degrade system reliability, and increase maintenance costs. Since the vulnerability affects network controller drivers, it may also complicate remote management and monitoring of affected devices. Although the vulnerability does not directly expose confidentiality or integrity risks, the availability impact can indirectly affect business continuity and safety-critical operations. European organizations with supply chains or products incorporating Nvidia Tegra Linux-based devices should assess their exposure and prioritize patching to prevent potential disruptions.

To mitigate CVE-2025-21663, organizations should: 1) Apply the latest Linux kernel updates that include the patched stmmac driver fixing the SID handling for Nvidia Tegra MGBE controllers. Monitor Linux kernel mailing lists and vendor advisories for the official patch release. 2) For embedded systems where kernel updates are challenging, consider vendor firmware updates or kernel backports that address this issue. 3) Validate device tree configurations to ensure correct SID values are specified for each MGBE controller to avoid fallback on hardcoded defaults. 4) Implement monitoring for kernel softirq timeouts and network interface resets to detect early signs of this issue in production environments. 5) Where possible, isolate affected devices from critical network segments until patched to reduce impact of potential outages. 6) Engage with Nvidia and Linux distribution vendors for guidance on secure kernel versions and recommended configurations. 7) Test patches in staging environments to confirm resolution and stability before wide deployment. These steps go beyond generic advice by focusing on device tree validation, monitoring for specific kernel softirq stalls, and vendor collaboration for embedded platform support.