Vulnerability Intelligence Report
Microsoft Office Security Feature Bypass Vulnerability
CVE-2026-21509
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
CISA KEV
SSVC: Active Exploitation
CVSS Base Score
7.8
HIGH
Exploitability:1.9
Impact Score:5.9
EPSS Probability:72.15%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
—
Authentication
—
Weaponization
—
SSVC Action
—
Weaknesses (CWE)
CWE-807 ↗CWE-807: Reliance on Untrusted Inputs in a Security Decision
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Microsoft | Microsoft 365 Apps for Enterprise | 16.0.1 < https://aka.ms/OfficeSecurityReleases (affected) |
| Microsoft | Microsoft Office 2016 | 16.0.0 < 16.0.5539.1001 (affected) |
| Microsoft | Microsoft Office 2019 | 19.0.0 < 16.0.10417.20095 (affected) |
| Microsoft | Microsoft Office LTSC 2021 | 16.0.1 < https://aka.ms/OfficeSecurityReleases (affected) |
| Microsoft | Microsoft Office LTSC 2024 | 16.0.0 < https://aka.ms/OfficeSecurityReleases (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | Microsoft Corporation · Vendor · USA |
| Reserved | 2025-12-30T18:10:54 |
| Published | 2026-01-26T17:06:35 |
| Patch Date | 2026-01-26 |
| Last Updated | 2026-07-30T20:47:35 |
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