What’s Vulnerable › Vulnerabilities
CVE-2026-64909: Microsoft Office Remote Code Execution Vulnerability
- Severity: high (CVSS 7.8 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: 2026-08-11 · updated 2026-10-28
- Weakness: CWE-191
Description
Integer underflow (wrap or wraparound) in Microsoft Office allows an unauthorized attacker to execute code locally.
Affected products
- Microsoft 365 Apps: all versions
- Microsoft 365: all versions
- Microsoft Office 2016: all versions
- Microsoft Office 2019: all versions
- Microsoft Office 2021: all versions
- Microsoft Office LTSC 2024: all versions
- Microsoft 365 Apps: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
- Microsoft Office 365 for Mac: from 1.0.0 before 16.112.26081010 — fixed in 16.112.26081010
- 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 16.112.26081010 — fixed in 16.112.26081010
- Microsoft Office: from 16.0.0 before 16.0.5565.1001 — fixed in 16.0.5565.1001
- 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 16.112.26081010 — fixed in 16.112.26081010
How to fix
Upgrade to a fixed version: Microsoft 365 Apps https://aka.ms/OfficeSecurityReleases; Microsoft Office 365 for Mac 16.112.26081010; Microsoft Office LTSC 2021 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2024 16.112.26081010; Microsoft Office 16.0.5565.1001; Microsoft Office LTSC 2024 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2021 16.112.26081010. Check the vendor advisory for mitigations.
References
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