Integer Underflow in Microsoft Excel Enables Local Code Execution

Publication date: 2026-01-13

Last updated on: 2026-01-13

Assigner: Microsoft Corporation

Description

Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-01-13

Last Modified

2026-01-13

Generated

2026-07-06

AI Q&A

2026-01-14

EPSS Evaluated

2026-07-05

NVD

CVE-2026-20957

Affected Vendors & Products

Vendor	Product	Version / Range
microsoft	office_excel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-122	A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
CWE-191	The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

Attack-Flow Graph

Executive Summary

This vulnerability is an integer underflow (wrap or wraparound) in Microsoft Office Excel that allows an unauthorized attacker to execute code locally on the affected system. [1]

Impact Analysis

This vulnerability can allow an unauthorized attacker to execute code locally, potentially leading to full compromise of the affected system including confidentiality, integrity, and availability impacts. [1]

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