CVE-2026-21509
CISA KEV
ACT NOW
Priority: 0.00
BB Relevance:
10/100
Published: N/A
Modified: N/A
First seen: 2026-10-29
Status: pending_score
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.
CISA Known Exploited Vulnerability
Vendor / Product
Microsoft — Office
Date Added
2026-01-26
Remediation Due
2026-02-16
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