CVE-2026-40366: CWE-416: Use After Free in Microsoft Microsoft 365 Apps for Enterprise
Access of resource using incompatible type ('type confusion') in Microsoft Office Word allows an unauthorized attacker to execute code locally.
AI Analysis
Technical Summary
CVE-2026-40366 is a use-after-free vulnerability (CWE-416) in Microsoft Office Word component of Microsoft 365 Apps for Enterprise. The issue arises from access of a resource using an incompatible type (type confusion), which can lead to unauthorized local code execution. The vulnerability has a CVSS 3.1 base score of 8.4, indicating high impact on confidentiality, integrity, and availability. Microsoft has released an official fix and manages remediation for this cloud service. The affected version explicitly identified is 16.0.1.
Potential Impact
Successful exploitation allows an unauthorized attacker to execute code locally with high impact on confidentiality, integrity, and availability of the affected system. This could lead to full compromise of the affected Microsoft 365 Apps for Enterprise environment. No known exploits in the wild have been reported at this time.
Mitigation Recommendations
An official fix is available from Microsoft. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Users and administrators should ensure their Microsoft 365 Apps for Enterprise installations are updated to the fixed version as per Microsoft's advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40366.
CVE-2026-40366: CWE-416: Use After Free in Microsoft Microsoft 365 Apps for Enterprise
Description
Access of resource using incompatible type ('type confusion') in Microsoft Office Word allows an unauthorized attacker to execute code locally.
CVSS v3.1
Score 8.4high
Affected software
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-40366 is a use-after-free vulnerability (CWE-416) in Microsoft Office Word component of Microsoft 365 Apps for Enterprise. The issue arises from access of a resource using an incompatible type (type confusion), which can lead to unauthorized local code execution. The vulnerability has a CVSS 3.1 base score of 8.4, indicating high impact on confidentiality, integrity, and availability. Microsoft has released an official fix and manages remediation for this cloud service. The affected version explicitly identified is 16.0.1.
Potential Impact
Successful exploitation allows an unauthorized attacker to execute code locally with high impact on confidentiality, integrity, and availability of the affected system. This could lead to full compromise of the affected Microsoft 365 Apps for Enterprise environment. No known exploits in the wild have been reported at this time.
Mitigation Recommendations
An official fix is available from Microsoft. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Users and administrators should ensure their Microsoft 365 Apps for Enterprise installations are updated to the fixed version as per Microsoft's advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40366.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- microsoft
- Date Reserved
- 2026-04-11T23:06:15.614Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- official-fix
- Is Cloud Service
- true
- Vendor Advisory Urls
- [{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40366","vendor":"Microsoft"}]
Threat ID: 6a036550cbff5d861008c8f5
Added to database: 05/12/2026, 17:37:20 UTC
Last enriched: 06/19/2026, 17:36:50 UTC
Last updated: 07/31/2026, 19:22:58 UTC
Views: 54
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