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MEDIUM · 5.5

CVE-2026-21261

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

Vulnerability Description

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

CVSS Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE

Affected Products

VendorProductVersions
Microsoft365 Apps-
MicrosoftExcel2016
MicrosoftOffice2019
MicrosoftOffice Long Term Servicing Channel2021
MicrosoftOffice Online Server< 16.0.10417.20097

Related Weaknesses (CWE)

CWE-125

References

FAQ

What is CVE-2026-21261?

CVE-2026-21261 is a vulnerability with a CVSS score of 5.5 (MEDIUM). Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.

How severe is CVE-2026-21261?

CVE-2026-21261 has been rated MEDIUM with a CVSS base score of 5.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-21261?

Check the references section above for vendor advisories and patch information. Affected products include: Microsoft 365 Apps, Microsoft Excel, Microsoft Office, Microsoft Office Long Term Servicing Channel, Microsoft Office Online Server.