What’s Vulnerable › Vulnerabilities

CVE-2026-40363: Microsoft Office Remote Code Execution Vulnerability

• Severity: high (CVSS 8.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% 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-122

Description

Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.

Affected products

• Microsoft 365 Apps: all versions
• Microsoft 365 Copilot: before 16.0.19822.20190 — fixed in 16.0.19822.20190
• Microsoft Office: 2016, 2019
• Microsoft Office LTSC for Mac 2021: 2021, 2024
• Microsoft 365 Apps: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office for Android: from 16.0.1 before 16.0.19822.20190 — fixed in 16.0.19822.20190
• 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 Office: from 16.0.0 before 16.0.5552.1000 — fixed in 16.0.5552.1000
• 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

How to fix

Upgrade to a fixed version: Microsoft 365 Copilot 16.0.19822.20190; Microsoft 365 Apps https://aka.ms/OfficeSecurityReleases; Microsoft Office for Android 16.0.19822.20190; Microsoft Office LTSC 2021 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2024 16.109.26051019; Microsoft Office 16.0.5552.1000; Microsoft Office LTSC 2024 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2021 16.109.26051019. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40363

Get alerted when CVE-2026-40363 or the next vulnerability affects your stack