What’s Vulnerable › Vulnerabilities

CVE-2026-45463: 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: 2026-06-09 · updated 2026-09-24
• 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 Copilot: 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 16.110.26061317 — fixed in 16.110.26061317
• Microsoft Office for Android: from 16.0.1 before 16.0.20131.20024 — fixed in 16.0.20131.20024
• 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 16.110.26061317 — fixed in 16.110.26061317
• Microsoft Office: from 16.0.0 before 16.0.5556.1005 — fixed in 16.0.5556.1005
• 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 16.110.26061317 — fixed in 16.110.26061317

How to fix

Upgrade to a fixed version: Microsoft 365 Apps https://aka.ms/OfficeSecurityReleases; Microsoft Office 365 for Mac 16.110.26061317; Microsoft Office for Android 16.0.20131.20024; Microsoft Office LTSC 2021 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2024 16.110.26061317; Microsoft Office 16.0.5556.1005; Microsoft Office LTSC 2024 https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC for Mac 2021 16.110.26061317. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45463

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