Heap-based Buffer Overflow in Microsoft Office Word
CVE-2026-78521

8.8HIGH

Key Information:

Vendor

Microsoft
Status
Microsoft 365 Apps For Enterprise
Microsoft Office 2019
Microsoft Office 365 For Mac
Microsoft Office Ltsc 2021
Vendor
CVE Published:
8 September 2026

What is CVE-2026-78521?

A heap-based buffer overflow vulnerability in Microsoft Office Word allows unauthorized attackers to potentially execute arbitrary code via crafted documents. This exposure occurs when processing specially crafted files, which can lead to unauthorized actions on the system of affected users. It’s essential for users to apply the latest patches and updates to mitigate risks associated with this vulnerability.

Affected Version(s)

Microsoft 365 Apps for Enterprise 32-bit Systems 16.0.1 < 16.0.20326.20138

Microsoft Office 2019 32-bit Systems 19.0.0 < 16.0.10417.20207

Microsoft Office 365 for Mac -

References

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

CVSS V3.1

Score:
8.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.