CVE-2025-29973 is a high-severity vulnerability classified under CWE-284 (Improper Access Control) affecting Microsoft Azure File Sync version 1.0.0. The vulnerability allows an authorized attacker with local access and low privileges to escalate their privileges on the affected system. Azure File Sync is a service that centralizes file shares in Azure while keeping the flexibility, performance, and compatibility of an on-premises file server. Improper access control in this context means that the software does not adequately enforce restrictions on what authenticated users can do, enabling them to perform actions beyond their intended permissions. The CVSS 3.1 score of 7.0 reflects a scenario where the attacker requires local access (AV:L), high attack complexity (AC:H), low privileges (PR:L), and no user interaction (UI:N). The impact affects confidentiality, integrity, and availability (all rated high), indicating that the attacker could potentially access sensitive data, modify or delete files, or disrupt service availability. The scope remains unchanged (S:U), meaning the exploit affects only the vulnerable component without extending to other system components. No known exploits are currently reported in the wild, and no patches have been published yet. This vulnerability was reserved in March 2025 and published in May 2025, indicating recent discovery and disclosure.

For European organizations, this vulnerability poses significant risks, especially for enterprises relying on Azure File Sync to manage hybrid cloud storage environments. Successful exploitation could lead to unauthorized access to sensitive corporate data, data tampering, or disruption of file synchronization services. This could impact business continuity, data integrity, and compliance with data protection regulations such as GDPR. Organizations in sectors with strict data confidentiality requirements—such as finance, healthcare, and government—are particularly vulnerable. Additionally, the need for local access means that insider threats or attackers who have already compromised a low-privilege account could leverage this vulnerability to escalate privileges and move laterally within the network. This elevates the risk of broader compromise and data breaches. The lack of user interaction requirement facilitates automated or stealthy exploitation once local access is obtained.

Given the absence of an official patch, European organizations should implement several specific mitigations: 1) Restrict and monitor local access to systems running Azure File Sync, enforcing strict access controls and using endpoint security solutions to detect unauthorized local activity. 2) Employ the principle of least privilege rigorously, ensuring users and service accounts have only the minimum necessary permissions to reduce the attack surface. 3) Use network segmentation to isolate file sync servers from general user workstations and limit lateral movement opportunities. 4) Enable and monitor detailed auditing and logging on Azure File Sync servers to detect unusual privilege escalations or access patterns. 5) Consider deploying application whitelisting and behavior-based detection tools to identify attempts to exploit access control weaknesses. 6) Stay alert for official patches or advisories from Microsoft and plan prompt deployment once available. 7) Conduct internal security awareness training emphasizing the risks of local access compromise and privilege escalation.