CVE-2025-21345 is a high-severity use-after-free vulnerability (CWE-416) affecting Microsoft Office 2019, specifically within the Microsoft Office Visio component. A use-after-free vulnerability occurs when a program continues to use a pointer after the memory it points to has been freed, potentially leading to arbitrary code execution, memory corruption, or system crashes. In this case, the vulnerability allows remote code execution (RCE) when a user opens a specially crafted Visio file. The CVSS 3.1 base score of 7.8 indicates a high severity, with an attack vector classified as local (AV:L), meaning the attacker must have local access to the system. However, no privileges are required (PR:N), and user interaction is necessary (UI:R), such as opening a malicious file. The vulnerability impacts confidentiality, integrity, and availability, as successful exploitation can lead to full system compromise. The vulnerability was published on January 14, 2025, and no known exploits are currently in the wild. No official patches or mitigation links are provided yet, suggesting that organizations should be vigilant and prepare to deploy updates once available. The vulnerability affects Microsoft Office 2019 version 19.0.0, which remains widely used in enterprise environments. Given the nature of the vulnerability, attackers could craft malicious Visio files distributed via email or other file-sharing methods to target users. This vulnerability is particularly dangerous because it can lead to remote code execution without requiring elevated privileges, relying only on user interaction to open a malicious file. The lack of known exploits in the wild currently reduces immediate risk but does not diminish the urgency for mitigation due to the potential impact.

For European organizations, the impact of CVE-2025-21345 could be significant. Microsoft Office 2019 is extensively deployed across various sectors including government, finance, healthcare, and critical infrastructure in Europe. Exploitation could lead to unauthorized access to sensitive data, disruption of business operations, and potential lateral movement within networks. Confidentiality breaches could expose personal data protected under GDPR, leading to regulatory penalties and reputational damage. Integrity and availability impacts could disrupt workflows and critical services, especially in sectors relying heavily on Office Visio for diagramming and planning. The requirement for local access and user interaction somewhat limits the attack surface but does not eliminate risk, as phishing campaigns remain a common vector for delivering malicious documents. The absence of known exploits currently provides a window for proactive defense, but the high severity score necessitates prompt attention to prevent future exploitation, especially given the strategic importance of European organizations in global supply chains and digital infrastructure.

1. Implement strict email filtering and attachment scanning to detect and block malicious Visio files before reaching end users. 2. Educate users on the risks of opening unsolicited or unexpected Visio documents, emphasizing phishing awareness and safe handling of email attachments. 3. Employ application whitelisting and sandboxing techniques to restrict execution of untrusted Office files. 4. Monitor endpoint behavior for signs of exploitation attempts, such as unusual process activity or memory anomalies related to Office applications. 5. Prepare for rapid deployment of official patches from Microsoft once released; maintain an up-to-date inventory of affected Office 2019 installations. 6. Utilize endpoint detection and response (EDR) solutions capable of detecting use-after-free exploitation patterns. 7. Restrict local access to critical systems and enforce least privilege principles to minimize the risk of local exploitation. 8. Consider disabling or limiting Visio file handling capabilities in environments where it is not essential, reducing the attack surface.