CVE-2026-21509
Microsoft Office Security Feature Bypass Vulnerability
Microsoft Office Security Feature Bypass Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.
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.
CISA notes
Please adhere to Microsoft’s recommended guidelines to address this vulnerability. Implement all final mitigations provided by the vendor for Office 2021, and apply the interim corresponding mitigations for Office 2016 and Office 2019 until the final patch becomes available. For more information please see: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509 ; https://nvd.nist.gov/vuln/detail/CVE-2026-21509
Description
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Severity
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:CAffected Products
| Vendor | Product | Affected versions |
|---|---|---|
| Microsoft | Microsoft 365 Apps for Enterprise | 16.0.1 to <https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office 2016 | 16.0.0 to <16.0.5539.1001 |
| Microsoft | Microsoft Office 2019 | 19.0.0 to <16.0.10417.20095 |
| Microsoft | Microsoft Office LTSC 2021 | 16.0.1 to <https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office LTSC 2024 | 16.0.0 to <https://aka.ms/OfficeSecurityReleases |
References
3 LinksRecord Details
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Related Tool Categories
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