CVE-2025-29822 is a high-severity vulnerability identified in Microsoft Office 2019, specifically affecting the OneNote component. The root cause of this vulnerability is an incomplete list of disallowed inputs, which leads to a security feature bypass. This vulnerability is categorized under CWE-184, which relates to incomplete or incorrect access control or input validation mechanisms. The flaw allows an unauthorized attacker to bypass security controls locally on the affected system. The CVSS 3.1 base score is 7.8, indicating a high severity level. The vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C indicates that the attack requires local access (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but does require user interaction (UI:R). The scope remains unchanged (S:U), and the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). The exploitability is currently unknown in the wild, and no patches have been linked yet. The vulnerability allows attackers to bypass security features, potentially leading to unauthorized data access, modification, or disruption of availability within the OneNote application environment. This could be leveraged for privilege escalation or to facilitate further local attacks.

For European organizations, this vulnerability poses a significant risk due to the widespread use of Microsoft Office 2019 in corporate, governmental, and educational environments. The ability to bypass security features locally could enable attackers to access sensitive information stored or processed within OneNote, compromise data integrity, or disrupt availability of critical note-taking and collaboration tools. This could lead to data breaches involving personal, financial, or intellectual property information, regulatory non-compliance (e.g., GDPR), and operational disruptions. Since the attack requires local access and user interaction, the threat is more pronounced in environments where endpoint security is weak or where social engineering tactics might be used to trick users into triggering the exploit. The high impact on confidentiality, integrity, and availability underscores the potential for serious damage, especially in sectors handling sensitive or regulated data.

European organizations should implement a multi-layered mitigation strategy beyond generic patching advice. First, restrict local access to systems running Microsoft Office 2019 OneNote to trusted users only, employing strict access controls and endpoint security solutions. Implement application whitelisting and behavior monitoring to detect anomalous activities indicative of exploitation attempts. Educate users about the risks of interacting with untrusted content or prompts within OneNote to reduce the likelihood of user interaction-based exploitation. Employ network segmentation to limit lateral movement if a local compromise occurs. Since no official patches are currently linked, organizations should monitor Microsoft’s security advisories closely and prioritize deployment of updates once available. Additionally, consider deploying endpoint detection and response (EDR) tools capable of identifying exploitation attempts related to input validation bypasses. Finally, conduct regular security audits and penetration testing focused on local privilege escalation and input validation weaknesses to proactively identify and remediate similar vulnerabilities.