Code execution via incompatible resource type access
Published May 12, 2026 · Updated May 12, 2026
Type confusion in Microsoft Word across affected Microsoft 365 Apps and Office releases allows local users to execute arbitrary code. Word accesses a resource through an incompatible object type, corrupting memory state during local processing; Microsoft has not disclosed the affected function or object class. Exploitation requires local access but no existing account privileges or user interaction, and successful exploitation runs code in the Word process context.
Summary
What happened
Type confusion in Microsoft Word across affected Microsoft 365 Apps and Office releases allows local users to execute arbitrary code. Word accesses a resource through an incompatible object type, corrupting memory state during local processing; Microsoft has not disclosed the affected function or object class. Exploitation requires local access but no existing account privileges or user interaction, and successful exploitation runs code in the Word process context.
The record
- CVE
- CVE-2026-40366
- Published
- May 12, 2026
- Updated
- May 12, 2026
- Vendor
- Microsoft
- Product
- Microsoft Office LTSC for Mac 2024
- Classifications
- CWE-416, T1203
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 12, 2026CVE publishedPublication date reported by the CVE source.
- May 12, 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 <16.109.26051019
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.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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