CVE-2026-21509: Microsoft Office Security Feature Bypass Vulnerability
In CISA’s Known Exploited Vulnerabilities catalog: Microsoft Office Security Feature Bypass Vulnerability.
Added , federal remediation due . Known ransomware use: Unknown.
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.
Description
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C · CWE-807
Status incidents that name it
No tracked status incident names this CVE.
Affected vendors and products
Microsoft: Microsoft 365 Apps for EnterpriseMicrosoft: Microsoft Office 2016Microsoft: Microsoft Office 2019Microsoft: Microsoft Office LTSC 2021Microsoft: Microsoft Office LTSC 2024
References
- CVE record on cve.org (opens in new tab)
- NVD entry (opens in new tab)
- msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509 (opens in new tab)
- CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (opens in new tab)
- This product uses data from the NVD API but is not endorsed or certified by the NVD. (opens in new tab)
- Known Exploited Vulnerabilities catalog from CISA. (opens in new tab)
- EPSS scores from FIRST (Exploit Prediction Scoring System). (opens in new tab)