Local security feature bypass
Published Jan 26, 2026 · Updated Jan 26, 2026
Security decision flaw in Microsoft Office allows local users to bypass a security feature by supplying untrusted input. Microsoft has not disclosed the affected component, the specific input trusted for the decision, or the protection that the input controls. Exploitation requires local access and user interaction; the resulting action and affected data or execution boundary remain undisclosed.
Summary
What happened
Security decision flaw in Microsoft Office allows local users to bypass a security feature by supplying untrusted input. Microsoft has not disclosed the affected component, the specific input trusted for the decision, or the protection that the input controls. Exploitation requires local access and user interaction; the resulting action and affected data or execution boundary remain undisclosed.
The record
- CVE
- CVE-2026-21509
- Published
- Jan 26, 2026
- Updated
- Jan 26, 2026
- Vendor
- Microsoft
- Product
- Microsoft Office 2016
- Classifications
- CWE-807
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 26, 2026Exploitation reportedCISA Known Exploited Vulnerabilities Catalog listing
- Jan 26, 2026CVE publishedPublication date reported by the CVE source.
- Jan 26, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=16.0.0 <16.0.5539.1001
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- CISA Known Exploited Vulnerabilities Catalog listingknown exploited catalog
Technologies
Your stack
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Your stack
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