7.8
High
Exploited
CVE-2026-21509 Microsoft Office Security Feature Bypass Vulnerability
Active exploitation observed
· CISA KEV catalogue
Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Ransomware campaigns
Not observed so far
Weakness
CWE-807
Description
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| Microsoft Office 2019 16.0 | earliest → < 16.0.10417.20095 | 16.0.10417.20095 |
| Microsoft 365 Apps for Enterprise 16.0 | 16.0.1 → latest | No fix stated |
| Microsoft Office LTSC 2021 16.0 | 16.0.1 → latest | No fix stated |
| Microsoft Office LTSC 2024 16.0 | 16.0.0 → latest | No fix stated |
| Microsoft Office 2016 16.0 | 16.0.0 → < 16.0.5539.1001 | 16.0.5539.1001 |
References
- Microsoft Office Security Feature Bypass Vulnerability msrc.microsoft.com
Timeline
- Published
- Added to the KEV catalogue
- Last modified
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