CVE-2026-55039

Analyzed Analyzed - Analysis Complete

Integer Underflow in Microsoft Office Excel Leads to Code Execution

Publication date: 2026-07-14

Last updated on: 2026-07-16

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

Probability:
Percentile:

Meta Information

Published

2026-07-14

Last Modified

2026-07-16

Generated

2026-08-04

AI Q&A

2026-07-15

EPSS Evaluated

2026-08-02

NVD

CVE-2026-55039

EUVD

EUVD-2026-44180

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	microsoft_365	*
microsoft	office_2021	*
microsoft	office_2021	*
microsoft	office_2021	*
microsoft	office_2024	*
microsoft	office_2024	*
microsoft	office_2024	*
microsoft	office_online_server	to 16.0.10417.20175 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
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.
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().

Attack-Flow Graph

Executive Summary

This vulnerability is an integer underflow in Microsoft Office Excel that allows an unauthorized attacker to execute code locally on a victim's system. An integer underflow occurs when a calculation results in a value smaller than the minimum representable integer, causing it to wrap around to a large positive number, potentially leading to memory corruption or arbitrary code execution.

Detection Guidance

This vulnerability involves an integer underflow in Microsoft Office Excel leading to remote code execution. Detection typically requires monitoring for suspicious Excel file processing or unusual system behavior. No specific commands are provided in the available resources.

Impact Analysis

This vulnerability could allow an attacker to run malicious code on your computer if you open a specially crafted Excel file. This could lead to unauthorized access to your system, data theft, installation of malware, or further compromise of your device and network.

Compliance Impact

This vulnerability could lead to unauthorized access or data breaches, which may violate compliance requirements under GDPR (data protection) or HIPAA (health information privacy). Organizations affected by such breaches may face legal penalties, fines, or reputational damage.

Mitigation Strategies

Apply the latest security updates from Microsoft for Microsoft Office Excel as soon as possible to patch the integer underflow vulnerability.

Hi! I’m here to help you understand CVE-2026-55039. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70