CVE-2025-21363 is a high-severity remote code execution vulnerability affecting Microsoft 365 Apps for Enterprise, specifically Microsoft Word version 16.0.1. The vulnerability is classified under CWE-822, which refers to untrusted pointer dereference. This type of flaw occurs when the software dereferences a pointer that can be influenced by an attacker, potentially leading to arbitrary code execution. In this case, the vulnerability allows an attacker to craft a malicious Word document that, when opened by a user, could trigger the dereference of an untrusted pointer. This can result in the execution of arbitrary code with the privileges of the current user. The CVSS v3.1 base score is 7.8, indicating a high severity level. The vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RC:C) shows that the attack requires local access (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but user interaction is necessary (UI:R). The scope is unchanged (S:U), and the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). The exploit code is currently not known to be in the wild, but the vulnerability is publicly disclosed and published on January 14, 2025. No patches or mitigation links are provided yet, indicating that organizations need to monitor for updates from Microsoft. This vulnerability poses a significant risk because it can lead to full system compromise if exploited, especially in environments where users frequently open Word documents from untrusted sources.

For European organizations, this vulnerability presents a considerable threat due to the widespread use of Microsoft 365 Apps for Enterprise across both private and public sectors. Successful exploitation could lead to unauthorized disclosure of sensitive information, data tampering, and disruption of business operations. Given the high impact on confidentiality, integrity, and availability, attackers could gain control over affected systems, potentially leading to lateral movement within networks and further compromise. Sectors such as finance, healthcare, government, and critical infrastructure, which rely heavily on Microsoft Office products, are particularly at risk. The requirement for user interaction means phishing or social engineering campaigns could be leveraged to deliver malicious documents. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, as attackers may develop exploits following public disclosure. The local attack vector suggests that attackers need some form of access to deliver the malicious document, but this is common in targeted attacks or insider threats. Overall, the vulnerability could facilitate espionage, data breaches, and operational disruptions within European organizations.

European organizations should implement a multi-layered defense strategy. First, they should enforce strict email filtering and attachment scanning to block or quarantine suspicious Word documents, especially from unknown or untrusted sources. User awareness training should be enhanced to educate employees about the risks of opening unsolicited or unexpected documents. Organizations should apply the principle of least privilege to limit user permissions, reducing the impact if exploitation occurs. Network segmentation can help contain potential breaches. Since no patch is currently available, organizations should monitor Microsoft security advisories closely and prioritize patch deployment once released. Employing endpoint detection and response (EDR) solutions can help detect anomalous behaviors indicative of exploitation attempts. Additionally, disabling macros and other active content in Word documents by default can reduce attack surface. Implementing application whitelisting and restricting execution of unauthorized code can further mitigate risk. Finally, organizations should review and update incident response plans to address potential exploitation scenarios involving Microsoft Word.