CVE-2026-40367: Microsoft Word Remote Code Execution Vulnerability

Severity: high (CVSS 8.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-12 · updated 2026-10-26
Weakness: CWE-822

Description

Access of resource using incompatible type ('type confusion') in Microsoft Office Word allows an unauthorized attacker to execute code locally.

Affected products

Microsoft 365 Apps: all versions
Microsoft Office: 2019
Microsoft Office LTSC for Mac 2021: 2021, 2024
Microsoft SharePoint Server: before 16.0.19725.20280; 2016, 2019 — fixed in 16.0.19725.20280
Microsoft Word for Android: 2016
Microsoft 365 Apps: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
Microsoft Office LTSC 2021: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
Microsoft Office LTSC for Mac 2024: from 16.0.0 before 16.109.26051019 — fixed in 16.109.26051019
Microsoft SharePoint Server Subscription Edition: from 16.0.0 before 16.0.19725.20280 — fixed in 16.0.19725.20280
Microsoft Word 2016: from 16.0.1 before 16.0.5552.1000 — fixed in 16.0.5552.1000
Microsoft Office: from 19.0.0 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
Microsoft Office LTSC 2024: from 16.0.0 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
Microsoft Office LTSC for Mac 2021: from 16.0.1 before 16.109.26051019 — fixed in 16.109.26051019
Microsoft Sharepoint Enterprise Server 2016: from 16.0.0 before 16.0.5552.1002 — fixed in 16.0.5552.1002
Microsoft SharePoint Server: from 16.0.0 before 16.0.10417.20128 — fixed in 16.0.10417.20128

How to fix

Upgrade to a fixed version: Microsoft SharePoint Server 16.0.19725.20280; Microsoft 365 Apps https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC 2021 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2024 16.109.26051019; Microsoft SharePoint Server Subscription Edition 16.0.19725.20280; Microsoft Word 2016 16.0.5552.1000; Microsoft Office https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC 2024 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2021 16.109.26051019; Microsoft Sharepoint Enterprise Server 2016 16.0.5552.1002; Microsoft SharePoint Server 16.0.10417.20128. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40367

Get alerted when CVE-2026-40367 or the next vulnerability affects your stack