Microsoft Office Zero-Day (CVE-2026-21509) - Emergency Patch Issued for Active Exploitation
Overview
Microsoft has released emergency patches for a serious vulnerability in Microsoft Office, identified as CVE-2026-21509. This zero-day flaw has a CVSS score of 7.8, indicating it is a significant security risk. The vulnerability allows attackers to bypass security features by exploiting untrusted inputs, potentially leading to unauthorized access. Organizations using affected Microsoft Office products should prioritize applying these patches, as the vulnerability is currently being exploited in the wild. This situation emphasizes the need for users to stay vigilant and maintain their software up to date to protect against such threats.
Key Takeaways
- Active Exploitation: This vulnerability is being actively exploited by attackers. Immediate action is recommended.
- Affected Systems: Microsoft Office products, particularly versions prone to the specific security feature bypass issue.
- Action Required: Microsoft has issued out-of-band security patches for the vulnerability.
- Timeline: Newly disclosed
Original Article Summary
Microsoft on Monday issued out-of-band security patches for a high-severity Microsoft Office zero-day vulnerability exploited in attacks. The vulnerability, tracked as CVE-2026-21509, carries a CVSS score of 7.8 out of 10.0. It has been described as a security feature bypass in Microsoft Office. "Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized
Impact
Microsoft Office products, particularly versions prone to the specific security feature bypass issue.
Exploitation Status
This vulnerability is confirmed to be actively exploited by attackers in real-world attacks. Organizations should prioritize patching or implementing workarounds immediately.
Timeline
Newly disclosed
Remediation
Microsoft has issued out-of-band security patches for the vulnerability. Users are advised to update their Office software immediately to the latest version to mitigate the risk.
Additional Information
This threat intelligence is aggregated from trusted cybersecurity sources. For the most up-to-date information, technical details, and official vendor guidance, please refer to the original article linked below.
Related Topics: This incident relates to CVE, Zero-day, Microsoft, and 2 more.