Heap-based Buffer Overflow in Microsoft Office Excel

Publication date: 2026-09-08

Last updated on: 2026-09-09

Assigner: Microsoft Corporation

Description

Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-08

Last Modified

2026-09-09

Generated

2026-09-29

AI Q&A

2026-09-09

EPSS Evaluated

2026-09-27

NVD

CVE-2026-81959

Affected Vendors & Products

Vendor	Product	Version / Range
microsoft	365_apps	*
microsoft	365_apps	*
microsoft	excel	2016
microsoft	excel	2016
microsoft	office_2019	*
microsoft	office_2019	*
microsoft	office_2016	*
microsoft	office_2016	*
microsoft	microsoft_365	*
microsoft	office_2021	*
microsoft	office_2021	*
microsoft	office_2021	*
microsoft	office_2024	*
microsoft	office_2024	*
microsoft	office_2024	*

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-190	The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

Attack-Flow Graph

Executive Summary

This is a heap-based buffer overflow vulnerability in Microsoft Office Excel. It allows an unauthorized attacker to execute arbitrary code on the affected system by exploiting a flaw in memory handling.

Impact Analysis

An attacker could exploit this to run malicious code on your computer, potentially stealing data, installing malware, or taking control of your system. It requires user interaction, such as opening a specially crafted Excel file.

Mitigation Strategies

Apply the latest security updates from Microsoft for affected Office Excel versions immediately. Disable Excel macros if not required and restrict user permissions to reduce attack surface.

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