CVE-2026-21514 is a vulnerability classified under CWE-807 (Reliance on Untrusted Inputs in a Security Decision) found in Microsoft 365 Apps for Enterprise, specifically Microsoft Word version 16.0.1. The flaw arises because the application improperly trusts input data when making security decisions, which can be manipulated by an unauthorized local attacker to bypass security controls. This bypass could allow the attacker to execute actions or access data that should be restricted, compromising confidentiality, integrity, and availability of the system. The vulnerability requires local access and user interaction but does not require privileges or authentication, making it easier to exploit in environments where users have physical or local access. The CVSS v3.1 score is 7.8 (high), reflecting the significant impact and exploitability. Although no public exploits are known yet, the vulnerability's nature and impact necessitate urgent attention. The absence of a patch link indicates that a fix may still be pending or in development. Organizations relying on Microsoft 365 Apps for Enterprise should monitor for updates and prepare to deploy patches promptly. The vulnerability highlights the risks of trusting unvalidated inputs in security decisions within widely used enterprise software.

This vulnerability can lead to unauthorized bypass of security features in Microsoft Word, potentially allowing attackers to access or manipulate sensitive documents, execute unauthorized actions, or disrupt availability. The impact spans confidentiality, integrity, and availability, which could result in data breaches, loss of data integrity, or denial of service conditions. Given Microsoft 365 Apps' widespread use in enterprises globally, exploitation could affect a large number of organizations, especially those with lax local access controls or where users might be tricked into interaction. The local attack vector limits remote exploitation but does not eliminate risk in environments with shared or poorly secured workstations. The high CVSS score indicates that the vulnerability is serious and could be leveraged in targeted attacks against enterprises, government agencies, and other organizations relying on Microsoft Office for critical workflows.

1. Immediately restrict local access to systems running the affected Microsoft 365 Apps version to trusted personnel only. 2. Implement strict endpoint security controls, including application whitelisting and user privilege restrictions, to limit the ability of unauthorized users to interact with Microsoft Word. 3. Educate users to avoid interacting with suspicious or unexpected prompts within Microsoft Word to reduce the risk of user interaction exploitation. 4. Monitor Microsoft security advisories closely for the release of patches addressing CVE-2026-21514 and prioritize rapid deployment once available. 5. Employ endpoint detection and response (EDR) solutions to detect anomalous local activities that could indicate exploitation attempts. 6. Consider using application sandboxing or virtualization technologies to isolate Microsoft Word processes and reduce the impact of potential bypasses. 7. Regularly audit and review local user permissions and access policies to minimize exposure. These measures go beyond generic patching advice by focusing on reducing the attack surface and limiting the conditions necessary for exploitation.