CVE-2025-29791 is a vulnerability classified under CWE-843 (Access of Resource Using Incompatible Type, commonly known as type confusion) affecting Microsoft 365 Apps for Enterprise, specifically version 16.0.1. The vulnerability occurs due to improper handling of resource types within the application, allowing an attacker to access resources using an incompatible type. This type confusion can be exploited by an unauthorized attacker to execute arbitrary code locally on the victim's machine. The attack vector requires local access and user interaction (e.g., opening a malicious document), but no prior privileges or authentication are necessary. The vulnerability impacts confidentiality, integrity, and availability, as arbitrary code execution can lead to full system compromise. The CVSS v3.1 base score is 7.8, reflecting high severity with local attack vector, low attack complexity, no privileges required, but user interaction needed. Although no public exploits are known at this time, the vulnerability poses a significant risk due to the ubiquity of Microsoft 365 in enterprise environments. The vulnerability was reserved in early March 2025 and published in April 2025, with no patch links currently available, indicating that remediation may still be pending or in progress. Organizations using the affected version should prioritize mitigation to prevent potential exploitation.

For European organizations, the impact of CVE-2025-29791 is substantial. Microsoft 365 Apps for Enterprise is widely used across Europe in both public and private sectors, including critical infrastructure, government agencies, and large enterprises. Successful exploitation could allow attackers to execute arbitrary code locally, potentially leading to data breaches, ransomware deployment, or disruption of business operations. The requirement for local access and user interaction somewhat limits remote exploitation but does not eliminate risk, as phishing or social engineering could facilitate initial access. The high confidentiality, integrity, and availability impact means sensitive corporate data and operational continuity could be severely affected. Organizations with less mature endpoint security or those that allow broad user privileges are particularly vulnerable. The absence of known exploits currently provides a window for proactive defense, but the threat landscape could evolve rapidly once exploit code becomes available.

1. Monitor Microsoft security advisories closely and apply official patches immediately once released for Microsoft 365 Apps for Enterprise version 16.0.1. 2. Implement strict application control policies (e.g., Microsoft Defender Application Control) to restrict execution of unauthorized code and scripts. 3. Enforce the principle of least privilege on user accounts to reduce the impact of local code execution. 4. Enhance endpoint detection and response (EDR) capabilities to identify suspicious behaviors indicative of exploitation attempts. 5. Conduct user awareness training focused on phishing and social engineering to reduce the likelihood of user interaction with malicious documents. 6. Utilize network segmentation to limit lateral movement if a local compromise occurs. 7. Temporarily restrict or monitor the use of Microsoft 365 Apps on high-risk endpoints until patches are applied. 8. Employ sandboxing or document viewing solutions that isolate potentially malicious files from the host environment. These measures, combined with timely patching, will reduce the risk and impact of exploitation.