CVE-2025-27752 is a heap-based buffer overflow vulnerability identified in Microsoft Office Excel 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 specially crafted Excel files. An unauthorized attacker can exploit this flaw by convincing a user to open a malicious Excel document, triggering the overflow and enabling the attacker to execute arbitrary code locally on the victim's machine. The vulnerability requires local access (attack vector: local), does not require privileges (PR:N), but does require user interaction (UI:R), such as opening the malicious file. The vulnerability affects confidentiality, integrity, and availability, with a CVSS v3.1 base score of 7.8 (high severity). The scope remains unchanged (S:U), meaning the exploit affects only the vulnerable component without impacting other system components. Although no known exploits are currently reported in the wild, the potential for local code execution makes this a significant threat, especially in environments where users frequently handle Excel files from untrusted sources. The lack of available patches at the time of publication increases the urgency for mitigation. This vulnerability is classified under CWE-122, which corresponds to heap-based buffer overflows, a common and dangerous class of memory corruption bugs that can lead to arbitrary code execution or system compromise.

For European organizations, the impact of CVE-2025-27752 can be substantial. Microsoft Office 2019 is widely used across Europe in both private and public sectors, including government agencies, financial institutions, healthcare providers, and enterprises. Successful exploitation could allow attackers to execute arbitrary code on user machines, potentially leading to data breaches, lateral movement within networks, or deployment of malware such as ransomware. The requirement for user interaction means phishing or social engineering campaigns could be leveraged to deliver malicious Excel files. Confidentiality is at risk due to possible data exfiltration, integrity could be compromised through unauthorized code execution, and availability might be affected if the exploit leads to system crashes or ransomware deployment. The local attack vector limits remote exploitation but does not diminish the threat in environments where users frequently exchange files. The absence of known exploits in the wild currently reduces immediate risk but does not preclude future exploitation, especially as threat actors often weaponize such vulnerabilities once disclosed. European organizations with high reliance on Microsoft Office 2019 and less mature endpoint protection or user awareness programs are particularly vulnerable.

1. Immediate mitigation should focus on user education to avoid opening Excel files from untrusted or unknown sources, especially those received via email or downloaded from the internet. 2. Implement strict email filtering and attachment scanning to detect and block potentially malicious Excel files before they reach end users. 3. Employ application whitelisting and endpoint protection solutions capable of detecting anomalous behavior related to memory corruption exploits. 4. Use Microsoft Office Protected View and enable macro restrictions to limit the execution of potentially harmful code within documents. 5. Monitor for unusual process behavior or crashes related to Excel, which could indicate exploitation attempts. 6. Maintain a robust patch management process and apply security updates promptly once Microsoft releases a patch for this vulnerability. 7. Consider deploying network segmentation to limit the spread of malware if exploitation occurs. 8. Use Data Loss Prevention (DLP) tools to monitor and prevent unauthorized data exfiltration that could result from exploitation. These steps go beyond generic advice by focusing on specific controls around file handling, user behavior, and monitoring tailored to this vulnerability's characteristics.