CVE-2025-21794 is a vulnerability identified in the Linux kernel specifically within the hid-thrustmaster driver, which handles Human Interface Devices (HID) related to Thrustmaster USB peripherals. The flaw is a stack-out-of-bounds read occurring in the usb_check_int_endpoints() function. This function processes an array named ep_addr, which is expected to be null-terminated to indicate the end of the array. However, the vulnerable code did not ensure a terminating zero element, causing the for loop in usb_check_int_endpoints() to read beyond the array's boundary. This out-of-bounds read leads to a kernel crash, resulting in a denial of service (DoS) condition. The root cause was detected by Syzbot, an automated kernel fuzzer, which identified the absence of a null element at the end of the ep_addr array. The fix involved appending a zero element to the array to properly terminate the loop and prevent out-of-bounds access. The vulnerability affects multiple versions of the Linux kernel as indicated by the commit hashes listed. There are no known exploits in the wild at the time of publication, and no CVSS score has been assigned yet. The vulnerability impacts kernel stability and availability but does not directly indicate privilege escalation or confidentiality breaches. However, kernel crashes can be leveraged in complex attack chains or cause significant disruption in critical systems.

For European organizations, the impact of CVE-2025-21794 primarily concerns system availability and stability. Organizations relying on Linux systems with the affected kernel versions and using Thrustmaster USB HID devices could experience kernel panics leading to unexpected reboots or service interruptions. This is particularly critical for sectors where uptime is essential, such as financial services, healthcare, telecommunications, and critical infrastructure. Although the vulnerability does not currently have known exploits, attackers could potentially use it to cause denial of service conditions, disrupting business operations or service delivery. In environments where Linux is used in embedded systems or industrial control systems, such instability could have safety or operational consequences. The vulnerability does not appear to allow privilege escalation or data leakage directly, but repeated crashes could be exploited as part of a broader attack strategy. European organizations with large Linux deployments, especially those using hardware peripherals from Thrustmaster or similar HID devices, should consider this vulnerability seriously to maintain operational continuity.

To mitigate CVE-2025-21794, European organizations should: 1) Apply the latest Linux kernel patches that include the fix for the hid-thrustmaster driver, ensuring the ep_addr array is properly null-terminated. 2) Conduct an inventory of Linux systems to identify those running affected kernel versions and assess whether Thrustmaster HID devices are in use. 3) Where immediate patching is not feasible, consider temporarily disabling or disconnecting Thrustmaster USB devices to prevent triggering the vulnerability. 4) Implement kernel crash monitoring and alerting to detect any unexpected panics potentially related to this vulnerability. 5) For critical systems, test patches in staging environments to ensure stability before deployment. 6) Maintain updated backups and recovery procedures to minimize downtime in case of kernel crashes. 7) Engage with hardware vendors and Linux distribution maintainers for guidance and updated drivers if custom or older kernels are in use. These steps go beyond generic advice by focusing on hardware-specific mitigation and operational continuity planning.