CVE-2025-59227 is a use-after-free vulnerability classified under CWE-416 affecting Microsoft Office 2016, specifically version 16.0.0. This vulnerability arises when the software improperly manages memory, freeing an object while it is still in use, which can lead to arbitrary code execution. An attacker can exploit this flaw to execute code locally on the victim’s machine without requiring privileges or authentication, but user interaction is necessary, such as opening a malicious document. The vulnerability affects confidentiality, integrity, and availability, potentially allowing attackers to run arbitrary code with the same privileges as the user, leading to data theft, system manipulation, or denial of service. The CVSS 3.1 base score is 7.8, indicating high severity, with attack vector local (AV:L), low attack complexity (AC:L), no privileges required (PR:N), and user interaction required (UI:R). 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 have been reported in the wild, and no patches have been released as of the publication date. The vulnerability was reserved on 2025-09-11 and published on 2025-10-14. Given the widespread use of Microsoft Office 2016 in enterprise environments, this vulnerability poses a significant risk, especially in environments where legacy software is still in use. The lack of a patch increases the urgency for organizations to implement interim mitigations and monitor for updates from Microsoft.

For European organizations, this vulnerability presents a substantial risk due to the widespread deployment of Microsoft Office 2016 in corporate, governmental, and educational institutions. Successful exploitation could lead to local code execution, enabling attackers to compromise sensitive data, disrupt business operations, or establish persistence within networks. The high impact on confidentiality, integrity, and availability means that critical documents and workflows could be manipulated or destroyed. Since exploitation requires user interaction, phishing or social engineering campaigns could be leveraged to trigger the vulnerability. The absence of a patch increases exposure time, potentially allowing attackers to develop exploits. Organizations relying on legacy Office versions without upgrade plans are particularly vulnerable. The threat is amplified in sectors with stringent data protection requirements under GDPR, where breaches could result in regulatory penalties and reputational damage.

1. Immediately audit and identify all instances of Microsoft Office 2016 version 16.0.0 within the organization. 2. Where feasible, upgrade to a supported and patched version of Microsoft Office to eliminate exposure to this vulnerability. 3. Until a patch is released, implement strict email filtering and attachment scanning to block potentially malicious documents. 4. Educate users about the risks of opening unsolicited or unexpected Office documents, emphasizing caution with email attachments and links. 5. Employ application whitelisting and endpoint protection solutions capable of detecting anomalous behavior indicative of exploitation attempts. 6. Use network segmentation to limit the impact of a compromised host. 7. Monitor security advisories from Microsoft closely and prepare for rapid deployment of patches once available. 8. Consider deploying sandboxing technologies to safely open suspicious documents in isolated environments. 9. Review and enhance incident response plans to address potential exploitation scenarios involving local code execution. 10. Disable or restrict macros and other potentially risky Office features where not required.