CVE-2025-9408 is a vulnerability identified in the Zephyr real-time operating system (RTOS), which is widely used in embedded systems and Internet of Things (IoT) devices. The flaw arises from a race condition during system call entry on Cortex M processors, where the privilege context switching mechanism does not properly synchronize, allowing malicious userspace processes to escalate their privileges. Although the description mentions Cortex R and A processors, the issue is primarily confirmed on Cortex M. This race condition can be exploited to gain kernel-level privileges from an unprivileged context, severely compromising system security. The vulnerability affects all versions of Zephyr, indicating a fundamental flaw in the system call handling implementation. The CVSS 3.1 score of 8.2 reflects a high severity, with the vector indicating local attack vector (AV:L), high attack complexity (AC:H), no privileges required (PR:N), no user interaction (UI:N), and a scope change (S:C) that impacts confidentiality, integrity, and availability (C:H/I:H/A:H). No known exploits are currently reported in the wild, but the practical nature of the race condition makes exploitation plausible. The vulnerability poses a significant risk to devices running Zephyr, especially those deployed in critical environments where unauthorized privilege escalation could lead to device takeover, data leakage, or denial of service.

For European organizations, the impact of CVE-2025-9408 is substantial, particularly for those relying on Zephyr-based embedded systems in critical infrastructure, industrial automation, automotive, healthcare devices, and IoT deployments. Successful exploitation could allow attackers to bypass security boundaries, execute arbitrary code with kernel privileges, and manipulate or disrupt device operations. This could lead to data breaches, operational downtime, safety hazards, and loss of trust in affected systems. Given the increasing adoption of Zephyr in European technology sectors, the vulnerability threatens confidentiality of sensitive data, integrity of system functions, and availability of essential services. The local attack vector limits remote exploitation, but insider threats or compromised devices could serve as attack entry points. The high attack complexity suggests that exploitation requires precise timing and conditions, but the absence of required privileges or user interaction lowers the barrier for attackers with local access. Overall, the vulnerability could undermine the security posture of embedded systems critical to European digital infrastructure.

To mitigate CVE-2025-9408, European organizations should prioritize the following actions: 1) Monitor Zephyr project communications and apply official patches or updates as soon as they become available, as no patch links are currently provided. 2) Restrict local access to devices running Zephyr by enforcing strong physical security and network segmentation to reduce the risk of local exploitation. 3) Implement strict access controls and authentication mechanisms on device interfaces to prevent unauthorized userspace code execution. 4) Employ runtime integrity monitoring and anomaly detection to identify suspicious privilege escalation attempts or unusual system call behavior. 5) Conduct thorough security audits of Zephyr-based devices in operational environments to identify and remediate potential exploitation vectors. 6) For critical deployments, consider additional hardware-based security features such as TrustZone or secure boot to limit the impact of privilege escalation. 7) Engage with vendors and suppliers to ensure timely vulnerability management and coordinated response. These targeted measures go beyond generic advice by focusing on access control, monitoring, and proactive patch management tailored to embedded system environments.