CVE-2026-21261

Microsoft Excel Information Disclosure Vulnerability

State: Published
Severity: 5.5 Medium
Published: Feb 10, 2026
Updated: Aug 19, 2026
Reserved: Dec 11, 2025

Description

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

Scores

CVSS	Score	Vector	Source
3.1	5.5 Medium	CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C	microsoft

Weaknesses

CWE-125 Out-of-bounds Read

Affected Products

Product	Versions
Microsoft 365 Apps for EnterpriseMicrosoft	16.0.1 to before https://aka.ms/OfficeSecurityReleasesAffected
Microsoft Excel 2016Microsoft	16.0.0.0 to before 16.0.5539.1002Affected
Microsoft Office 2019Microsoft	19.0.0 to before https://aka.ms/OfficeSecurityReleasesAffected
Microsoft Office LTSC 2021Microsoft	16.0.1 to before https://aka.ms/OfficeSecurityReleasesAffected
Microsoft Office LTSC 2024Microsoft	16.0.0 to before https://aka.ms/OfficeSecurityReleasesAffected
Microsoft Office LTSC for Mac 2021Microsoft	16.0.1 to before 16.106.26020821Affected
Microsoft Office LTSC for Mac 2024Microsoft	16.0.0 to before 16.106.26020821Affected
Office Online ServerMicrosoft	16.0.0.0 to before 16.0.10417.20097Affected

References

Microsoft Excel Information Disclosure Vulnerabilityvendor-advisorypatch

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