CVE-2026-21509
Microsoft Office Security Feature Bypass Vulnerability
CVSS
—
No CVSS
EPSS
72.2%
p99
KEV
YES
Jan 26, 2026
Exploit Today
80
0-100
Published: — · Last modified: —
Product
Microsoft / Office
Vulnerability
Microsoft Office Security Feature Bypass Vulnerability
Added to KEV
Jan 26, 2026
Remediate by
Feb 16, 2026
Known ransomware use
No
Summary 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.
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.
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