Microsoft Office Zero-Day Vulnerability: CVE-2026-21509

Microsoft has disclosed CVE-2026-21509, a high-severity security feature bypass vulnerability affecting Microsoft Office. This flaw could allow attackers to circumvent built-in protection mechanisms, increasing the risk of malicious document-based attacks. While Microsoft has released updates to mitigate the issue, organisations running Office in enterprise environments should ensure patch compliance immediately.

Security experts emphasise that vulnerabilities in widely deployed platforms like Office remain a key entry point for phishing, credential theft, and ransomware delivery.