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CVE-2021-40486: Microsoft Word Remote Code Execution Vulnerability

• Severity: medium (CVSS 6.8 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 6.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-10-13 · updated 2026-06-17

Description

Microsoft Word Remote Code Execution Vulnerability

Affected products

• Microsoft Office: 2019
• Microsoft Office Online Server: all versions
• Microsoft Office Web Apps Server: 2013-sp1
• Microsoft SharePoint Server: 2013-sp1, 2016
• Microsoft SharePoint Server: 2019
• Microsoft Word for Android: 2013-sp1, 2016
• Microsoft Office Web Apps Server 2013 Service Pack 1: from 15.0.1 before 15.0.5389.1000 — fixed in 15.0.5389.1000
• Microsoft SharePoint Enterprise Server 2013 Service Pack 1: from 15.0.0 before 15.0.5389.1000 — fixed in 15.0.5389.1000
• Microsoft Word 2013 Service Pack 1: from 15.0.1 before 15.0.5389.1000 — fixed in 15.0.5389.1000
• Microsoft Word 2016: from 16.0.1 before 16.0.5227.1000 — fixed in 16.0.5227.1000
• Microsoft Office: from 19.0.0 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office Online Server: from 16.0.1 before 16.0.10379.20000 — fixed in 16.0.10379.20000
• Microsoft Sharepoint Enterprise Server 2016: from 16.0.0 before 16.0.5227.1000 — fixed in 16.0.5227.1000
• Microsoft SharePoint Server: from 16.0.0 before 16.0.10379.20000 — fixed in 16.0.10379.20000

How to fix

Upgrade to a fixed version: Microsoft Office Web Apps Server 2013 Service Pack 1 15.0.5389.1000; Microsoft SharePoint Enterprise Server 2013 Service Pack 1 15.0.5389.1000; Microsoft Word 2013 Service Pack 1 15.0.5389.1000; Microsoft Word 2016 16.0.5227.1000; Microsoft Office https://aka.ms/OfficeSecurityReleases; Microsoft Office Online Server 16.0.10379.20000; Microsoft Sharepoint Enterprise Server 2016 16.0.5227.1000; Microsoft SharePoint Server 16.0.10379.20000. Check the vendor advisory for mitigations.

References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40486
• https://www.zerodayinitiative.com/advisories/ZDI-21-1158/
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40486
• https://www.zerodayinitiative.com/advisories/ZDI-21-1158/

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