CVE-2025-30393 is a high-severity use-after-free vulnerability identified in Microsoft 365 Apps for Enterprise, specifically affecting Microsoft Office Excel version 16.0.1. The vulnerability is classified under CWE-416, which refers to use-after-free errors where a program continues to use a pointer after the memory it points to has been freed. This flaw allows an unauthorized attacker to execute arbitrary code locally on the affected system. The vulnerability requires the attacker to have local access (AV:L), does not require privileges (PR:N), but does require user interaction (UI:R), such as opening a malicious Excel file. The scope is unchanged (S:U), meaning the impact is limited to the vulnerable component. The CVSS v3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability (all rated high). Exploitation could lead to full compromise of the affected system by executing arbitrary code with the privileges of the user running Excel. Although no known exploits are currently reported in the wild, the vulnerability is publicly disclosed and considered critical enough to warrant immediate attention. The lack of an official patch link suggests that remediation may be pending or that users should monitor for updates from Microsoft. The vulnerability arises from improper memory management in Excel, which can be triggered by specially crafted Excel files that exploit the use-after-free condition during document processing or rendering. This type of vulnerability is particularly dangerous because it can be exploited through social engineering, convincing users to open malicious documents, leading to local code execution without requiring elevated privileges initially.

For European organizations, this vulnerability poses a significant risk due to the widespread use of Microsoft 365 Apps for Enterprise across various sectors including government, finance, healthcare, and critical infrastructure. Successful exploitation could lead to unauthorized access, data theft, disruption of business operations, and potential lateral movement within corporate networks. Given the high confidentiality, integrity, and availability impacts, sensitive data could be exposed or altered, and systems could be rendered unstable or unusable. The requirement for user interaction means phishing campaigns or targeted spear-phishing attacks could be effective vectors, increasing the risk for organizations with large user bases or less mature security awareness programs. The local attack vector limits remote exploitation but does not eliminate risk, especially in environments where endpoint security is weak or where users have administrative privileges. The absence of known exploits in the wild currently provides a window for proactive mitigation, but the public disclosure increases the likelihood of future exploit development. European organizations must consider the regulatory implications of data breaches resulting from exploitation, including GDPR compliance and potential fines.

To mitigate this vulnerability effectively, European organizations should: 1) Immediately verify the version of Microsoft 365 Apps for Enterprise deployed and prioritize upgrading to a patched version once Microsoft releases an update addressing CVE-2025-30393. 2) Implement strict email filtering and attachment scanning to detect and block malicious Excel files, leveraging advanced threat protection solutions capable of sandboxing and behavioral analysis. 3) Enhance user awareness training focusing on the risks of opening unsolicited or suspicious Excel documents, emphasizing the importance of verifying the source before enabling content. 4) Enforce the principle of least privilege by ensuring users operate with minimal necessary permissions, reducing the impact of local code execution. 5) Deploy endpoint detection and response (EDR) tools to monitor for anomalous behavior indicative of exploitation attempts, such as unusual process spawning or memory manipulation. 6) Consider application control policies or sandboxing for Microsoft Office applications to limit the execution context of potentially malicious files. 7) Maintain up-to-date backups and incident response plans to quickly recover from any compromise. 8) Monitor threat intelligence feeds and Microsoft security advisories for updates on exploit availability and patches.