CVE-2025-12852 is a DLL loading vulnerability classified under CWE-427 (Uncontrolled Search Path Element) found in NEC Corporation's RakurakuMusen Start EX software, affecting all versions. This vulnerability allows an attacker with local access to manipulate the environment variables or directory structure that the software uses to locate DLLs, causing it to load malicious DLLs instead of legitimate ones. This can lead to arbitrary code execution or unintended operations on the user's device, compromising confidentiality, integrity, and availability. The CVSS 4.0 vector indicates local attack vector (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but user interaction is needed (UI:A). The vulnerability has high impact on confidentiality, integrity, and availability, with no scope change. Although no known exploits are currently reported in the wild and no patches have been released, the risk remains significant due to the ease of exploitation once local access is obtained. The vulnerability stems from improper handling of DLL search paths, which can be exploited by placing a malicious DLL in a directory that the application searches before the legitimate DLL location. This type of attack is particularly dangerous in environments where users might be tricked into opening files or applications that trigger the vulnerable software. The lack of patches necessitates immediate mitigation through environment hardening and monitoring.

For European organizations, this vulnerability poses a significant risk especially in environments where NEC RakurakuMusen Start EX is deployed, such as enterprise or governmental sectors relying on NEC's communication or software solutions. Exploitation could lead to unauthorized code execution, data leakage, or disruption of critical services. Since the attack requires local access and user interaction, insider threats or social engineering attacks could be vectors. The high impact on confidentiality, integrity, and availability means sensitive data could be exposed or systems could be destabilized, affecting business continuity. Given NEC's presence in European markets, particularly in Japan-Europe technology partnerships and sectors like telecommunications, manufacturing, and public services, the vulnerability could affect critical infrastructure and sensitive operations. The absence of patches increases the window of exposure, making proactive mitigation essential to prevent potential exploitation.

1. Restrict and harden the DLL search path by configuring the system to use fully qualified paths for DLL loading and avoid reliance on relative or environment-dependent paths. 2. Implement application whitelisting and code integrity checks to prevent unauthorized DLLs from loading. 3. Use Windows features such as SafeDllSearchMode to prioritize system directories over user or current directories. 4. Educate users to avoid opening untrusted files or applications that could trigger the vulnerable software. 5. Monitor system logs and use endpoint detection and response (EDR) tools to detect anomalous DLL loading behaviors. 6. Isolate systems running RakurakuMusen Start EX to limit local access and reduce attack surface. 7. Engage with NEC for updates and patches and prepare to deploy them promptly once available. 8. Conduct regular vulnerability assessments and penetration tests focusing on DLL hijacking vectors. 9. Apply least privilege principles to user accounts to minimize the impact of potential exploitation. 10. Consider deploying application sandboxing or virtualization to contain potential malicious code execution.