CVE-2025-64677 is a cross-site scripting (XSS) vulnerability classified under CWE-79, affecting the Microsoft Office Out-of-Box Experience (OOBE) component. The flaw stems from improper neutralization of user-supplied input during the generation of web pages within the OOBE process. This improper sanitization allows an unauthorized attacker to inject malicious scripts that can execute in the context of the affected application, leading primarily to spoofing attacks over a network. The vulnerability does not require any privileges or user interaction, making it easier to exploit remotely. The CVSS v3.1 score of 8.2 reflects a high severity, with network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction (UI:N). The impact is primarily on confidentiality (C:H), with limited integrity impact (I:L) and no availability impact (A:N). The vulnerability was reserved in early November 2025 and published in mid-December 2025, with no known exploits in the wild and no patches currently available. The OOBE component is typically involved during the initial setup and configuration of Microsoft Office products, which may expose systems during deployment or first-time use. Attackers exploiting this vulnerability could perform spoofing attacks, potentially misleading users or intercepting sensitive information during the setup process. Given the widespread use of Microsoft Office in enterprise environments, this vulnerability poses a significant risk, especially in scenarios where network defenses are weak or where OOBE is exposed to untrusted networks.

For European organizations, the impact of CVE-2025-64677 can be substantial due to the widespread deployment of Microsoft Office products across public and private sectors. The vulnerability's ability to be exploited remotely without authentication or user interaction increases the risk of large-scale attacks, particularly during device provisioning or software deployment phases. Confidentiality breaches could lead to exposure of sensitive corporate or personal data, undermining trust and compliance with regulations such as GDPR. Although the integrity and availability impacts are limited, the potential for spoofing attacks can facilitate phishing, social engineering, or further exploitation chains. Critical sectors such as finance, healthcare, government, and infrastructure that rely heavily on Microsoft Office are at heightened risk. Additionally, organizations with less mature network segmentation or endpoint protection may face increased exposure. The absence of patches at the time of disclosure necessitates immediate compensatory controls to mitigate risk until official fixes are deployed.

1. Limit network exposure of systems undergoing Office OOBE processes by isolating them within secure network segments or VLANs. 2. Employ strict firewall rules to restrict inbound and outbound traffic related to OOBE communications, especially from untrusted networks. 3. Monitor network traffic and logs for unusual or suspicious activity indicative of XSS exploitation attempts targeting OOBE components. 4. Educate IT staff and users about the risks associated with spoofing and phishing attacks that may leverage this vulnerability. 5. Implement endpoint protection solutions capable of detecting and blocking script-based attacks or anomalous behaviors during Office setup. 6. Prepare for rapid deployment of Microsoft patches once released by maintaining updated asset inventories and patch management processes. 7. Consider using application whitelisting or sandboxing techniques to limit the execution scope of Office OOBE processes. 8. Review and harden group policies and configuration management to minimize unnecessary exposure of OOBE interfaces. 9. Engage with Microsoft support channels for guidance and early access to mitigation tools or updates if available. 10. Conduct penetration testing or vulnerability assessments focused on Office deployment environments to identify and remediate exposure points.