Heap-based Buffer Overflow in Microsoft Office Excel
CVE-2026-21259

7.8HIGH

Key Information:

Vendor

Microsoft
Status
Microsoft 365 Apps For Enterprise
Microsoft Excel 2016
Microsoft Office 2019
Microsoft Office Ltsc 2021
Vendor
CVE Published:
10 February 2026

What is CVE-2026-21259?

A heap-based buffer overflow vulnerability in Microsoft Office Excel may allow an unauthorized attacker to escalate their privileges locally. This flaw can be exploited to manipulate Excel processes, posing a potential risk to system integrity. Users are advised to apply the latest security patches to mitigate the risks associated with this vulnerability, as it could lead to unauthorized access and control over system resources.

Affected Version(s)

Microsoft 365 Apps for Enterprise 32-bit Systems 16.0.1

Microsoft Excel 2016 32-bit Systems 16.0.0.0 < 16.0.5539.1002

Microsoft Office 2019 32-bit Systems 19.0.0

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE...
vendor-advisorypatch

CVSS V3.1

Score:
7.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.