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CVE-2026-21509

Microsoft Office Security Feature Bypass Vulnerability

Published: Jan 26, 2026Updated: Jun 25, 2026 Sources: CVE List NVD BDUCWE-807
7.8HIGH
NVD MITRE
EPSS Score
72.2%
Top 0.6%
CISA KEV
Active Exploitation
Since Jan 26, 2026
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

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

No summary for this CVE yet.

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
Open in CVSS calculator →

Weaknesses

CWE-807

Affected Products

Microsoft Corp
commercial·USaka microsoft, microsoft corporation
Microsoft 365 Apps for EnterpriseDesktop App
Consumer Software / productivity
Microsoft Office LTSC 2021Desktop App
Consumer Software / productivity
office long term servicing channelOn-premOS
Operating Systems / windows
and 10 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
Is your org exposed to CVE-2026-21509?We can run the check for you — a free external exposure review, no install. Check my exposure

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509
msrc.microsoft.com
https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerability
vicarius.io
https://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerability
vicarius.io
and 4 more references View all →
News mentions
5

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