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MEDIUM · 5.5

CVE-2026-21258

Improper input validation in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.

Vulnerability Description

Improper input validation 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-20CWE-125

References

FAQ

What is CVE-2026-21258?

CVE-2026-21258 is a vulnerability with a CVSS score of 5.5 (MEDIUM). Improper input validation in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.

How severe is CVE-2026-21258?

CVE-2026-21258 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-2026-21258?

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.