Is It On KEV?

Microsoft Office

YES - ON THE CISA KEV LIST
CVE-2026-21509

Microsoft Office Security Feature Bypass Vulnerability

CISA catalog due date2026-02-16
268 days past due
EPSS exploit probability (next 30 days)70.8% · 99percentile
From CVE publication to KEV listing0 days (2026-01-26 → 2026-01-26)
Remediation window (KEV listing to due date)21 days
Days on the KEV list289 days
Date added to KEV2026-01-26
Known ransomware campaign useUnknown
VendorMicrosoft
ProductOffice
Weaknesses (CWE)CWE-807

Microsoft: 391 entries (22.0% of all KEV entries are from this vendor); 41 added in 2026.

BOD 26-04 note: this is the date printed in the CISA catalog. A federal agency's actual deadline is set by its SSVC tier - Act (3 days), Attend (14 days), Track (60 days), or the next scheduled upgrade - counted from the KEV listing date or the date the vulnerability is identified in its environment, whichever comes first. Use the tier helper on each CVE page for your own window.

Your BOD 26-04 window (SSVC tier helper)

Your remediation window ends:

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 (CISA)

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

References

Other KEV entries for this vendor: Microsoft

Microsoft - Vendors with KEV entries

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