CVE-2026-21509 — Microsoft Office Security Feature Bypass Vulnerability
2026-01-26 • CISA Known Exploited Vulnerability
[event] 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.
> AFFECTED SOFTWARE
| Field | Value |
|---|---|
| Vendor | Microsoft |
| Product | Office |
| CWE | CWE-807 |
| CVE ID | CVE-2026-21509 |
| Date Added | 2026-01-26 |
| Due Date | 2026-02-16 |
| Ransomware Campaign | Unknown |
> MITIGATION
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Due Date: 2026-02-16