What’s Vulnerable › Vulnerabilities

CVE-2021-34478: Microsoft Office Remote Code Execution Vulnerability

• Severity: medium (CVSS 6.8 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 51.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-08-12 · updated 2026-08-10

Description

Microsoft Office Remote Code Execution Vulnerability

Affected products

• Microsoft 365 Apps: all versions
• Microsoft Office: 2019
• Microsoft 365 Apps: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office: from 19.0.0 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases

How to fix

Upgrade to a fixed version: Microsoft 365 Apps https://aka.ms/OfficeSecurityReleases; Microsoft Office https://aka.ms/OfficeSecurityReleases. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34478
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34478
• https://www.zerodayinitiative.com/advisories/ZDI-21-1024/

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