CVE-2025-54638 is a medium-severity vulnerability identified in Huawei's HarmonyOS versions 5.1.0 and 5.0.1. The issue stems from inconsistent read/write serialization within the advertising (ad) module of the operating system. Specifically, it involves CWE-502, which is the deserialization of untrusted data. Deserialization vulnerabilities occur when untrusted input is deserialized without sufficient validation, potentially allowing attackers to manipulate the deserialization process. In this case, the inconsistent serialization and deserialization logic in the ad module can be exploited to disrupt the normal functioning of the ad service. The vulnerability does not impact confidentiality or integrity but affects availability, as successful exploitation can cause denial of service or service disruption of the ad service component. The CVSS 3.1 base score is 5.5, reflecting a medium severity with the vector AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, meaning the attack requires local access with low complexity, low privileges, no user interaction, and impacts availability only. No known exploits have been reported in the wild, and no patches have been linked yet. The vulnerability was published on August 6, 2025, and was reserved on July 28, 2025. This vulnerability is significant because the ad module is a core component that may be integrated into various HarmonyOS devices, and disruption could degrade user experience or device functionality related to advertising services.

For European organizations using Huawei devices running HarmonyOS 5.0.1 or 5.1.0, this vulnerability could lead to service disruptions in the ad module, potentially affecting applications or services relying on advertising components. While the impact is limited to availability and does not compromise data confidentiality or integrity, denial of service conditions can degrade user experience and may indirectly affect revenue streams for businesses dependent on ad services. In sectors where Huawei devices are used extensively, such as telecommunications, smart devices, or IoT deployments, this could lead to operational interruptions. Additionally, if the ad module is integrated into critical consumer or enterprise devices, repeated exploitation could cause reputational damage or increased support costs. However, the requirement for local access and low privileges limits remote exploitation, reducing the risk of widespread attacks. The absence of user interaction simplifies exploitation in controlled environments but restricts large-scale remote attacks.

To mitigate this vulnerability, European organizations should: 1) Monitor Huawei's official security advisories closely for patches or updates addressing CVE-2025-54638 and apply them promptly once available. 2) Restrict local access to devices running affected HarmonyOS versions by enforcing strict physical security and limiting user privileges to trusted personnel only. 3) Implement application whitelisting and integrity checks on the ad module to detect unauthorized modifications or abnormal behavior. 4) Employ runtime monitoring tools to detect anomalies in the ad service that could indicate exploitation attempts. 5) Where feasible, consider upgrading to newer HarmonyOS versions not affected by this vulnerability or deploying alternative devices for critical operations. 6) Educate users and administrators about the risks of local exploitation and enforce policies to minimize exposure to untrusted code or data inputs within the ad module context. 7) Conduct regular security audits and penetration tests focusing on local privilege escalation and deserialization attack vectors within the device environment.