CVE-2025-54910 is a heap-based buffer overflow vulnerability identified in Microsoft Office 2019 (version 19.0.0). This vulnerability arises from improper handling of memory allocation on the heap, which can lead to an overflow condition when processing certain crafted inputs. Exploiting this flaw allows an unauthorized attacker to execute arbitrary code locally on the affected system without requiring any user interaction or prior authentication. The vulnerability is classified under CWE-122, indicating a heap-based buffer overflow, which is a common and critical memory corruption issue. The CVSS v3.1 base score is 8.4, reflecting a high severity level. The vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C) indicates that the attack requires local access (AV:L), has low attack complexity (AC:L), requires no privileges (PR:N), and no user interaction (UI:N). The scope is unchanged (S:U), and the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). No known exploits are currently reported in the wild, and no official patches have been linked yet. This vulnerability could be triggered by processing malicious Office documents, potentially delivered via local means such as removable media or local network shares. Given the lack of user interaction and privileges required, this vulnerability poses a significant risk to systems where Microsoft Office 2019 is installed and accessible to untrusted local users or processes.

For European organizations, the impact of CVE-2025-54910 can be substantial. Microsoft Office 2019 remains widely used across various sectors including government, finance, healthcare, and education throughout Europe. The ability for an attacker to execute arbitrary code locally without user interaction or privileges can lead to full system compromise, data exfiltration, lateral movement within networks, and disruption of critical business operations. Confidentiality breaches could expose sensitive personal data protected under GDPR, leading to regulatory penalties and reputational damage. Integrity and availability impacts could disrupt document workflows and critical business processes. The local attack vector suggests that insider threats or attackers gaining limited local access could exploit this vulnerability to escalate privileges or establish persistence. The absence of known exploits in the wild currently provides a window for proactive mitigation, but the high severity score and ease of exploitation underscore the urgency for European organizations to address this vulnerability promptly.

1. Immediate deployment of any official patches or security updates from Microsoft once available is critical. 2. Until patches are released, restrict local access to systems running Microsoft Office 2019 to trusted users only, and enforce strict access controls on shared resources and removable media. 3. Employ application whitelisting and endpoint protection solutions capable of detecting anomalous behavior indicative of exploitation attempts. 4. Monitor local system logs and security events for unusual activity related to Office processes. 5. Educate users and administrators about the risk of opening untrusted documents locally and enforce policies to minimize the use of external media. 6. Consider upgrading to newer versions of Microsoft Office that may have improved security controls and mitigations. 7. Implement network segmentation to limit the spread of potential compromises originating from exploited local systems. 8. Use advanced threat detection tools that can identify heap-based buffer overflow exploitation techniques. These targeted measures go beyond generic advice by focusing on limiting local attack vectors, enhancing detection, and preparing for rapid patch deployment.