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CVE-2026-21509

Microsoft Office Security Feature Bypass Vulnerability

Published: Jan 26, 2026Updated: Feb 11, 2026 Sources: CVE List NVD BDU
7.8CVSS
HIGH

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

EPSS Score
12.1%
Top 6.1%
CISA KEV
Active Exploitation
Since Jan 26, 2026
Exploits
No Known Exploits
Remediation
Patch Available

CVSS Vector Breakdown

AV:LAC:LPR:NUI:RS:UC:HI:HA:H
Exploitability
AV:LAttack Vector
Local
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High

Weaknesses

Affected Products

Microsoft 365 Apps for Enterprise
Microsoft
Microsoft Office 2016
Microsoft
Microsoft Office 2019
Microsoft
Microsoft Office LTSC 2021
Microsoft
Microsoft Office LTSC 2024
Microsoft
and 8 more affected products View all →

Exploitability

CISA Known Exploited Vulnerability
Added to KEV:Jan 26, 2026
Remediation due:Feb 16, 2026

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.

Official Patch Available
Workaround Available

References

and 4 more references View all →

Timeline

Added to CISA KEV
Jan 26, 2026
Published
Jan 26, 2026
Last Updated
Feb 11, 2026
5

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