CVE-2025-21346 is a high-severity security vulnerability identified in Microsoft Office 2019, specifically version 19.0.0. The vulnerability is classified under CWE-693, which pertains to Protection Mechanism Failure. This indicates that a security feature designed to protect the application or its data can be bypassed or is ineffective. The CVSS 3.1 base score of 7.1 reflects a high impact, with the vector indicating that the attack requires local access (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but does require user interaction (UI:R). The scope is unchanged (S:U), meaning the vulnerability affects only the vulnerable component. The impact metrics show no confidentiality impact (C:N), but high integrity (I:H) and availability (A:H) impacts, meaning an attacker can significantly alter or disrupt data or functionality without leaking confidential information. The exploitability is rated as official (RC:C) with no known exploits in the wild at the time of publication. The vulnerability likely allows an attacker to bypass security features within Office 2019, potentially enabling malicious code execution, data corruption, or denial of service. Since the attack vector is local, an attacker must have access to the victim machine and induce user interaction, such as opening a malicious document or triggering a specific Office feature. The lack of patch links suggests that a fix may not yet be publicly available, increasing the urgency for mitigation.

For European organizations, this vulnerability poses a significant risk due to the widespread use of Microsoft Office 2019 across enterprises, government agencies, and critical infrastructure sectors. The high integrity and availability impact means attackers could manipulate or disrupt critical documents, workflows, or automated processes relying on Office files, potentially leading to operational downtime or data integrity issues. Since the attack requires local access and user interaction, insider threats or targeted phishing campaigns could exploit this vulnerability to escalate attacks within networks. Sectors such as finance, healthcare, and public administration, which heavily depend on Office documents for sensitive data and regulatory compliance, are particularly vulnerable. The absence of known exploits currently reduces immediate risk, but the availability of detailed vulnerability information could lead to rapid development of exploit code, increasing the threat landscape. Additionally, disruption or corruption of Office files could impact business continuity and trust in document authenticity, which is critical for legal and contractual processes in Europe.

European organizations should implement a multi-layered mitigation approach beyond generic patching advice. First, restrict local access to systems running Office 2019 by enforcing strict endpoint security policies, including least privilege access and device control. Deploy application whitelisting to prevent unauthorized execution of potentially malicious Office macros or scripts. Enhance user awareness training focusing on the risks of opening untrusted documents and recognizing phishing attempts that could trigger this vulnerability. Utilize advanced endpoint detection and response (EDR) solutions to monitor for anomalous Office behaviors indicative of exploitation attempts. Since no patch is currently available, consider deploying Office 2019 in a hardened configuration, disabling unnecessary features or macros where feasible. Network segmentation can limit lateral movement if an attacker gains local access. Finally, maintain up-to-date backups of critical documents and systems to recover from potential data integrity or availability attacks.