Integer Underflow Vulnerability in Microsoft Office Allows Unauthorized Local Code Execution
CVE-2026-64909

7.8HIGH

Key Information:

Vendor

Microsoft
Status
Microsoft 365 Apps For Enterprise
Microsoft Office 2016
Microsoft Office 2019
Microsoft Office 365 For Mac
Vendor
CVE Published:
11 August 2026

What is CVE-2026-64909?

An integer underflow vulnerability in Microsoft Office can be exploited by unauthorized attackers to execute arbitrary code on the affected system. This issue creates conditions where input values do not properly validate, allowing for potential manipulation of system resources and unauthorized actions within the operating environment. Users are advised to apply relevant patches to mitigate the risk associated with this vulnerability.

Affected Version(s)

Microsoft 365 Apps for Enterprise 32-bit Systems 16.0.1

Microsoft Office 2016 32-bit Systems 16.0.0 < 16.0.5565.1001

Microsoft Office 2019 32-bit Systems 19.0.0

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE...
vendor-advisorypatch

CVSS V3.1

Score:
7.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.