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CVE-2026-21509: Microsoft Office Security Feature Bypass Vulnerability
Microsoft Office · in CISA KEV since 2026-01-26
2026-01-26added to KEV
2026-02-16federal remediation due date
72.87%EPSS exploit probability (30 days) 99.4th percentile
7.8 HIGHCVSS 3.1
Unknownknown ransomware use
0days from NVD publication to KEV
What it is
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 action (CISA)
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
| CWE | CWE-807 |
|---|---|
| CVSS vector | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
| NVD published | 2026-01-26 (Analyzed) |
Original records: NVD · CISA KEV · JSON: /api/cve/CVE-2026-21509.json · all KEV CVEs
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Get the full file: Exploited Vulnerabilities Brief – September 2026 ($29): this month's KEV additions ranked by EPSS, ransomware use and due date, ready to hand to a patch team. Checkout by Polar.
Get the full file: Exploited Vulnerabilities Brief – September 2026 ($29): this month's KEV additions ranked by EPSS, ransomware use and due date, ready to hand to a patch team. Checkout by Polar.