CVE-2026-66809

Analyzed Analyzed - Analysis Complete

Out-of-bounds Read in Microsoft Office

Publication date: 2026-08-11

Last updated on: 2026-08-14

Assigner: Microsoft Corporation

Description

Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-11

Last Modified

2026-08-14

Generated

2026-09-01

AI Q&A

2026-08-11

EPSS Evaluated

2026-08-30

NVD

CVE-2026-66809

EUVD

EUVD-2026-56752

Affected Vendors & Products

Vendor	Product	Version / Range
microsoft	365_apps	*
microsoft	365_apps	*
microsoft	word	2016
microsoft	word	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	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-125	The product reads data past the end, or before the beginning, of the intended buffer.

Attack-Flow Graph

Executive Summary

This is an out-of-bounds read vulnerability in Microsoft Office. It allows an unauthorized attacker to access and disclose information stored locally on a system by reading beyond the intended memory boundaries of the application.

Detection Guidance

This vulnerability is an out-of-bounds read in Microsoft Office that allows local information disclosure. Detection typically involves checking for unusual behavior in Office applications or scanning for known indicators of compromise. Use Microsoft's official tools like Microsoft Defender for Endpoint to scan for related threats. Ensure all Office applications are updated to the latest patched versions.

Impact Analysis

An attacker could exploit this to read sensitive data from your system, such as documents or files, without needing special permissions. This could lead to unauthorized access to confidential information stored on your device.

Compliance Impact

This vulnerability could lead to unauthorized data disclosure, which may violate compliance requirements such as GDPR or HIPAA if sensitive personal or health information is exposed. Organizations must address it to maintain regulatory compliance.

Mitigation Strategies

Apply the latest security updates from Microsoft Office as soon as possible to patch the out-of-bounds read vulnerability.

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