CVE-2025-66331 is a vulnerability identified in Huawei's HarmonyOS, specifically in the office service component. The root cause is classified under CWE-494, which involves the download of code without performing integrity checks. This flaw allows an attacker to cause a denial of service (DoS) condition by potentially introducing malformed or malicious code that disrupts the normal operation of the office service, thereby impacting system availability. The affected versions include HarmonyOS 5.0.1, 5.1.0, and 6.0.0. According to the CVSS 3.1 scoring, the vulnerability has a low severity score of 3.3, with an attack vector limited to local access (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The scope is unchanged (S:U), and the impact is limited to availability (A:L) without affecting confidentiality or integrity. No known exploits have been reported in the wild, and no patches have been published yet. The vulnerability indicates a lack of integrity verification when downloading code modules or updates within the office service, which can be exploited to crash or halt the service, leading to denial of service. This vulnerability highlights the importance of implementing cryptographic integrity checks such as digital signatures or hashes when downloading executable code or modules to prevent tampering or corruption.

For European organizations, the primary impact of CVE-2025-66331 is the potential disruption of availability in systems running Huawei HarmonyOS office services. This could lead to temporary denial of service conditions affecting productivity and operational continuity, especially in environments relying on HarmonyOS for office-related tasks. Since the vulnerability requires local access and user interaction, the risk is somewhat mitigated in well-controlled environments but remains a concern in scenarios where insider threats or social engineering attacks are possible. The lack of confidentiality or integrity impact reduces the risk of data breaches or unauthorized data modification. However, critical sectors such as government, telecommunications, and enterprises using Huawei devices could experience service interruptions, which might have cascading effects on business operations. The absence of known exploits and patches currently limits immediate risk but also underscores the need for proactive monitoring and mitigation.

To mitigate CVE-2025-66331, European organizations should implement the following specific measures: 1) Restrict local access to devices running HarmonyOS by enforcing strict physical and logical access controls, including multi-factor authentication and endpoint security solutions. 2) Educate users to avoid interacting with suspicious prompts or downloads related to the office service to reduce the risk of exploitation requiring user interaction. 3) Monitor system logs and network activity for unusual behavior or crashes related to the office service that could indicate attempted exploitation. 4) Employ application whitelisting and integrity verification tools where possible to detect unauthorized code modifications or downloads. 5) Coordinate with Huawei for timely updates and patches, and plan for rapid deployment once available. 6) Consider network segmentation to isolate critical HarmonyOS devices and limit the spread of potential DoS impacts. 7) Develop incident response plans that include scenarios involving denial of service on HarmonyOS devices to ensure quick recovery.