CVE-2025-26629 is a use-after-free vulnerability classified under CWE-416 affecting Microsoft 365 Apps for Enterprise version 16.0.1. Use-after-free vulnerabilities occur when a program continues to use memory after it has been freed, leading to undefined behavior such as arbitrary code execution. In this case, the vulnerability allows an unauthorized attacker to execute code locally on the victim's machine by exploiting improper memory handling within Microsoft Office components. The CVSS v3.1 base score of 7.8 reflects a high severity, with attack vector local (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The scope is unchanged (S:U), and the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). This means an attacker can fully compromise the affected system's data and functionality once the vulnerability is exploited. Although no public exploits are known at this time, the vulnerability poses a significant risk due to the widespread use of Microsoft 365 Apps in enterprise environments. The vulnerability was reserved in February 2025 and published in March 2025, indicating recent discovery and disclosure. The lack of available patches at the time of this report suggests organizations must implement interim mitigations until official updates are released. The vulnerability is particularly dangerous because it does not require authentication, only user interaction, such as opening a malicious document, which is a common attack vector in phishing campaigns targeting enterprise users.

For European organizations, the impact of CVE-2025-26629 is substantial. Microsoft 365 Apps for Enterprise is widely deployed across Europe in both public and private sectors, including government, finance, healthcare, and critical infrastructure. Exploitation could lead to local code execution, enabling attackers to install malware, steal sensitive data, or disrupt business operations. The high impact on confidentiality, integrity, and availability means that data breaches, ransomware deployment, or system outages are plausible consequences. Given the requirement for user interaction, phishing or social engineering campaigns could be leveraged to trigger exploitation. The absence of known exploits currently provides a window for proactive defense, but the vulnerability's nature and severity make it a prime target for attackers once exploit code becomes available. Organizations with remote or hybrid workforces using Microsoft 365 Apps on personal or unmanaged devices may face increased risk. Additionally, regulatory compliance frameworks such as GDPR impose strict data protection requirements, and exploitation could lead to significant legal and financial repercussions for affected European entities.

1. Monitor Microsoft security advisories closely and apply official patches immediately upon release to remediate the vulnerability. 2. Until patches are available, implement application control policies to restrict execution of untrusted or unsigned code within Microsoft 365 Apps environments. 3. Enforce the principle of least privilege by limiting user permissions to reduce the impact of local code execution. 4. Educate users on phishing risks and suspicious document handling to minimize successful exploitation via social engineering. 5. Employ endpoint detection and response (EDR) solutions to detect anomalous behaviors indicative of exploitation attempts. 6. Disable or restrict macros and other potentially dangerous Office features where feasible. 7. Use network segmentation to isolate critical systems and limit lateral movement in case of compromise. 8. Regularly back up critical data and verify recovery procedures to mitigate ransomware or destructive attacks stemming from exploitation. 9. Conduct threat hunting exercises focusing on indicators of use-after-free exploitation patterns within Microsoft 365 Apps. 10. Collaborate with cybersecurity information sharing groups to stay informed about emerging exploits and attack trends related to this vulnerability.