Integer Underflow Vulnerability in Microsoft Office Excel
CVE-2026-20957

7.8HIGH

Key Information:

Vendor

Microsoft
Status
Office Online Server
Microsoft Office 2019
Microsoft 365 Apps For Enterprise
Microsoft Office Ltsc For Mac 2021
Vendor
CVE Published:
13 January 2026

What is CVE-2026-20957?

An integer underflow vulnerability exists in Microsoft Office Excel that can allow an unauthorized attacker to execute arbitrary code locally. This type of exploit might occur during specific calculations or data manipulations, leading to a potential compromise of the system's integrity. Immediate action is crucial to safeguard against this risk.

Affected Version(s)

Microsoft 365 Apps for Enterprise 32-bit Systems 16.0.1

Microsoft Excel 2016 32-bit Systems 16.0.0.0 < 16.0.5535.1000

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

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