Microsoft Office Security Feature Bypass Vulnerability
Description
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.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Turn on Microsoft alerts
Details
- Vendor
- Microsoft
- Product
- Microsoft Office
- CVE
- CVE-2026-21509
- Affected versions
- Microsoft 365 Apps: version not specified
Office 2016: Office 2016
Office 2019: Office 2019
Office LTSC 2021: Office LTSC 2021
Office LTSC 2024: Office LTSC 2024 (from the advisory and NVD; check the exact builds in the official advisory) - CVSS score
- 7.8
- Actively exploited
- Yes, listed in the CISA Known Exploited Vulnerabilities catalog
- CISA due date
- February 16, 2026 (deadline for US federal agencies: a good benchmark for you too)
- Source
- CISA KEV – original advisory
- Published
- January 26, 2026
The description and the recommended action are quoted from the public advisory; severity, exploitation status and affected versions are compiled automatically from public sources and may contain errors. The vendor's original advisory prevails: check it before taking action. This information is provided without warranty and does not replace a professional assessment.