CVE-2025-30377 is a high-severity use-after-free vulnerability identified in Microsoft Office 2019, specifically version 19.0.0. This vulnerability is categorized under CWE-416, which involves the use of memory after it has been freed, leading to undefined behavior. In this case, an unauthorized attacker can exploit this flaw to execute arbitrary code locally on the affected system without requiring any user interaction or privileges. The vulnerability arises because the application continues to use a pointer to memory that has already been deallocated, allowing attackers to manipulate program execution flow, potentially leading to full system compromise. The CVSS 3.1 base score of 8.4 reflects the critical nature of this vulnerability, with high impact on confidentiality, integrity, and availability (all rated high), and low attack complexity. The attack vector is local, meaning the attacker must have local access to the system, but no privileges or user interaction are required, increasing the risk in environments where local access is possible. Although no known exploits are currently reported in the wild, the vulnerability is publicly disclosed and could be targeted by attackers once exploit code becomes available. The lack of an official patch at the time of publication increases the urgency for organizations to implement mitigations and monitor for updates from Microsoft.

For European organizations, the impact of CVE-2025-30377 could be significant, especially in sectors relying heavily on Microsoft Office 2019 for daily operations, such as government agencies, financial institutions, healthcare providers, and large enterprises. Successful exploitation could lead to unauthorized code execution, resulting in data breaches, system compromise, and disruption of critical business processes. The high impact on confidentiality, integrity, and availability means sensitive information could be exposed or altered, and systems could be rendered inoperable. Since the attack requires local access but no privileges or user interaction, insider threats or attackers who gain physical or remote local access (e.g., through compromised credentials or lateral movement) could leverage this vulnerability to escalate privileges or deploy malware. This elevates risks in environments with shared workstations, remote desktop services, or insufficient endpoint security controls. Additionally, the absence of known exploits currently provides a window for proactive defense, but also means organizations must be vigilant for emerging threats targeting this vulnerability.

Given the absence of an official patch at the time of disclosure, European organizations should implement several specific mitigations: 1) Restrict local access to systems running Microsoft Office 2019 by enforcing strict access controls and monitoring for unauthorized physical or remote local logins. 2) Employ application whitelisting and endpoint detection and response (EDR) solutions to detect and block suspicious behaviors indicative of exploitation attempts. 3) Harden user privileges by ensuring users operate with the least privilege necessary, reducing the likelihood of successful exploitation from local access. 4) Disable or restrict use of legacy or vulnerable Office features that may be involved in the vulnerability, if identified by Microsoft advisories. 5) Monitor security advisories from Microsoft closely and prepare for rapid deployment of patches once available. 6) Conduct user awareness training to reduce insider threat risks and encourage reporting of suspicious activity. 7) Implement network segmentation to limit lateral movement opportunities for attackers who gain local access. These targeted mitigations, combined with standard security hygiene, will reduce the attack surface and exposure until a patch is released.