Summary
| Parameter | Value |
|---|---|
| CVE ID | CVE-2026-21509 |
| CVE Publication Year | 2026 |
| Date Added to CISA KEV | 2026-01-26 |
| Vendor | Microsoft |
| Product | Office |
| CVSS Score | 7.8 (high) |
| CISA KEV Status | Yes - confirmed active exploitation |
| Ransomware | Not confirmed |
| Remediation Deadline | 2026-02-16 |
Vulnerability Description
Microsoft Office contains a security feature bypass vulnerability in which reliance on untrusted inputs in a security decision in Microsoft Office could allow an unauthorized attacker to bypass a security feature locally. Some of the impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.
Required Actions
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Who Is Affected?
This vulnerability affects Office by Microsoft. Check if your organization uses this software and requires updates.
Sources
Need help securing your systems? nFlo team offers vulnerability management services. Contact us.
How can nFlo help?
If your organization uses products affected by this vulnerability, contact us. We can help with:
- Verifying whether your systems are at risk
- Implementing patches and risk mitigation
- Monitoring for exploitation attempts in your environment
Useful resources:
