CVE-2025-9408 is a vulnerability identified in the Zephyr real-time operating system (RTOS), specifically affecting the system call entry mechanism on Cortex M processors. The issue arises from a race condition during the privilege context switching process, which is a critical operation that transitions execution from unprivileged userspace to privileged kernel mode. This race condition allows a malicious userspace process to escalate its privileges by exploiting timing windows in the system call entry code path. While the vulnerability is confirmed on Cortex M, it may not affect Cortex R or A architectures. The flaw impacts all versions of Zephyr, indicating a fundamental design or implementation issue in the context switching mechanism. The CVSS v3.1 base score is 8.2, reflecting high severity with a 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 affects confidentiality, integrity, and availability (C:H/I:H/A:H). This means an attacker with local access to the device can exploit the race condition without needing prior privileges or user interaction, potentially gaining full control over the system. Although no exploits have been reported in the wild yet, the vulnerability's nature makes it a critical concern for embedded systems using Zephyr, especially in safety-critical or security-sensitive environments. The lack of available patches at the time of reporting necessitates immediate attention from vendors and users to develop and deploy fixes.

For European organizations, the impact of CVE-2025-9408 is significant, particularly for those deploying Zephyr RTOS in embedded systems such as industrial control systems, automotive electronics, medical devices, and IoT infrastructure. Successful exploitation can lead to complete system compromise, allowing attackers to bypass security controls, manipulate device behavior, exfiltrate sensitive data, or cause denial of service. This threatens operational continuity, data confidentiality, and system integrity. Given the increasing reliance on embedded devices in critical infrastructure and manufacturing sectors across Europe, the vulnerability poses risks to national security, economic stability, and public safety. Organizations in sectors like energy, transportation, healthcare, and manufacturing must consider the potential for targeted attacks exploiting this flaw. The local attack vector implies that attackers need some form of local access, which could be achieved through physical access, compromised supply chains, or lateral movement within networks. The high attack complexity may limit widespread exploitation but does not eliminate the risk for well-resourced adversaries.

Mitigation should begin with monitoring vendor communications for official patches addressing CVE-2025-9408 and applying them promptly once available. In the interim, organizations should implement strict access controls to limit local access to devices running Zephyr, including physical security measures and network segmentation to reduce the attack surface. Employ runtime protections such as process isolation and integrity monitoring to detect anomalous behavior indicative of exploitation attempts. Conduct thorough code audits and testing for custom Zephyr-based applications to identify and remediate potential exploitation vectors. Where feasible, disable or restrict system call interfaces that are not essential to reduce exposure. Additionally, implement secure boot and firmware integrity verification to prevent unauthorized code execution. Regularly update device firmware and maintain an inventory of all Zephyr deployments to prioritize remediation efforts. Finally, enhance incident response capabilities to quickly detect and respond to potential exploitation attempts.