CVE-2026-78521

HIGH CVSS 3.1: 8.8 EPSS 0.82%
Updated Sep 17, 2026
Microsoft
Parameter Value
CVSS 8.8 (HIGH)
Type CWE-122 (Heap-based Buffer Overflow)
Vendor Microsoft
Public PoC No

Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
Required
User action required

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service

CVSS Vector v3.1

Vulnerable Products 13

Configuration From (including) Up to (excluding)
Microsoft 365_Apps
cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:*
— —
Microsoft 365_Apps
cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x86:*
— —
Microsoft Microsoft_365
cpe:2.3:a:microsoft:microsoft_365:-:*:*:*:*:macos:*:*
— —
Microsoft Office_2019
cpe:2.3:a:microsoft:office_2019:-:*:*:*:*:*:x64:*
— —
Microsoft Office_2019
cpe:2.3:a:microsoft:office_2019:-:*:*:*:*:*:x86:*
— —
Microsoft Office_2021
cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x64:*
— —
Microsoft Office_2021
cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x86:*
— —
Microsoft Office_2021
cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:macos:-:*
— —
Microsoft Office_2024
cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x64:*
— —
Microsoft Office_2024
cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x86:*
— —
Microsoft Office_2024
cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:macos:-:*
— —
Microsoft Word
cpe:2.3:a:microsoft:word:2016:*:*:*:*:*:x64:*
— —
Microsoft Word
cpe:2.3:a:microsoft:word:2016:*:*:*:*:*:x86:*
— —