CVE-2025-53741 is a heap-based buffer overflow vulnerability classified under CWE-122, found in Microsoft Office Online Server's Excel processing component (version 16.0.0.0). This vulnerability allows an attacker to execute arbitrary code locally without requiring privileges but does require user interaction, such as opening a maliciously crafted Excel file via the Office Online Server interface. The flaw arises from improper handling of heap memory during Excel file processing, leading to memory corruption that can be exploited to execute code with the privileges of the Office Online Server process. The vulnerability has a CVSS 3.1 base score of 7.8, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity and no privileges required. Although no public exploits are known at this time, the vulnerability is critical due to the widespread deployment of Office Online Server in enterprise environments for collaborative document editing and sharing. The vulnerability's exploitation could lead to unauthorized code execution, data leakage, or service disruption. Microsoft has not yet released patches, but organizations are advised to monitor updates closely. The vulnerability's requirement for user interaction limits remote exploitation but does not eliminate risk, especially in targeted phishing or social engineering attacks. The Office Online Server is often integrated into enterprise environments, making lateral movement and privilege escalation possible if exploited.

For European organizations, the impact of CVE-2025-53741 can be significant. Exploitation could lead to unauthorized code execution on servers hosting Office Online Server, potentially compromising sensitive corporate data and disrupting business operations. Given the integration of Office Online Server in many enterprise collaboration environments, a successful attack could facilitate lateral movement within networks, leading to broader compromise. Confidentiality is at high risk due to potential data leakage, integrity can be compromised by unauthorized modification of documents or system files, and availability may be affected by service crashes or denial of service conditions. The requirement for user interaction means phishing campaigns targeting European employees could be a vector for exploitation. Organizations in sectors such as finance, government, and critical infrastructure, which heavily rely on Microsoft collaboration tools, face heightened risks. The absence of known exploits currently provides a window for proactive defense, but the high severity score necessitates urgent attention to patching and mitigation.

1. Monitor Microsoft security advisories closely and apply patches for Office Online Server 16.0.0.0 immediately upon release. 2. Restrict access to Office Online Server interfaces to trusted networks and users only, using network segmentation and firewalls. 3. Implement strict email filtering and user awareness training to reduce the risk of phishing attacks that could deliver malicious Excel files. 4. Employ application whitelisting and endpoint protection solutions on servers hosting Office Online Server to detect and block suspicious code execution. 5. Enable detailed logging and monitoring on Office Online Server to detect anomalous activities indicative of exploitation attempts. 6. Consider disabling or limiting Excel file processing capabilities in Office Online Server if not required. 7. Use multi-factor authentication for access to Office Online Server management interfaces to prevent unauthorized changes. 8. Conduct regular vulnerability assessments and penetration testing focused on Office Online Server deployments to identify and remediate weaknesses.