What’s Vulnerable › Vulnerabilities

CVE-2026-66806: Microsoft Office Word Information Disclosure Vulnerability

• Severity: medium (CVSS 5.5 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: 2026-08-11 · updated 2026-10-30
• Weakness: CWE-193

Description

Off-by-one error in Microsoft Office Word allows an unauthorized attacker to disclose information locally.

Affected products

• Microsoft 365 Apps: all versions
• Microsoft Office 2019: all versions
• Microsoft Office 2021: all versions
• Microsoft Office LTSC 2024: all versions
• Microsoft Word for Android: 2016
• Microsoft 365 Apps: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office LTSC 2021: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Word 2016: from 16.0.1 before 16.0.5565.1000 — fixed in 16.0.5565.1000
• Microsoft Office: from 19.0.0 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office LTSC 2024: from 16.0.0 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 LTSC 2021 https://aka.ms/OfficeSecurityReleases; Microsoft Word 2016 16.0.5565.1000; Microsoft Office https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC 2024 https://aka.ms/OfficeSecurityReleases. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66806

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