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CVE-2026-21509
HIGHCISA KEV7.8
Description
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
CVE Details
CVSS v3.1 Score7.8
SeverityHIGH
CVSS VectorCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack VectorLOCAL
ComplexityLOW
Privileges RequiredNONE
User InteractionREQUIRED
Published1/26/2026
Last Modified2/11/2026
Sourcekev
Honeypot Sightings0
CISA KEV
VendorMicrosoft
ProductOffice
Vulnerability NameMicrosoft Office Security Feature Bypass Vulnerability
KEV Date Added2026-01-26
Remediation Due Date2026-02-16
Ransomware UseUnknown
Affected Products
microsoft:365_appsmicrosoft:officemicrosoft:office_long_term_servicing_channel
Weaknesses (CWE)
CWE-807
References
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509(secure@microsoft.com)
https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerability(af854a3a-2127-422b-91ae-364da2661108)
https://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerability(af854a3a-2127-422b-91ae-364da2661108)
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21509(134c704f-9b21-4f2e-91b3-4a467353bcc0)
IOC Correlations
No correlations recorded
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