CVE-2026-78510

Microsoft Outlook and Word Remote Code Execution Vulnerability

Published Sep 8, 2026 CVSS 3.1 · 8.4 High EPSS < 1% KEV · Not listed

Description

Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Microsoft

Microsoft 365 Apps for Enterprise

affected

Version	Status	Constraints
`16.0.1`	affected	< 16.0.20326.20138

Microsoft

Microsoft Office 2016

affected

Version	Status	Constraints
`16.0.0`	affected	< 16.0.5569.1000

Microsoft

Microsoft Office 2019

affected

Version	Status	Constraints
`19.0.0`	affected	< 16.0.10417.20207

Microsoft

Microsoft Office 365 for Mac

affected

Version	Status	Constraints
`1.0.0`	affected	< 16.113.26091433

Microsoft

Microsoft Office LTSC 2021

affected

Version	Status	Constraints
`16.0.1`	affected	< 16.0.14334.20906

Microsoft

Microsoft Office LTSC 2024

affected

Version	Status	Constraints
`16.0.0`	affected	< 16.0.17932.20976

Microsoft

Microsoft Office LTSC for Mac 2021

affected

Version	Status	Constraints
`16.0.1`	affected	< 16.113.26091433

Microsoft

Microsoft Office LTSC for Mac 2024

affected

Version	Status	Constraints
`16.0.0`	affected	< 16.113.26091433

Configuration 1 [-]

OR	cpe:2.3:a:microsoft:365_apps:-::::enterprise::x64:*
	cpe:2.3:a:microsoft:365_apps:-::::enterprise::x86:*
	cpe:2.3:a:microsoft:microsoft_365:-:::::macos::
	cpe:2.3:a:microsoft:office_2016:-::::-::x64:*
	cpe:2.3:a:microsoft:office_2016:-::::-::x86:*
	cpe:2.3:a:microsoft:office_2019:-::::::x64:
	cpe:2.3:a:microsoft:office_2019:-::::::x86:
	cpe:2.3:a:microsoft:office_2021:-::::ltsc:-:x64:
	cpe:2.3:a:microsoft:office_2021:-::::ltsc:-:x86:
	cpe:2.3:a:microsoft:office_2021:-::::ltsc:macos:-:
	cpe:2.3:a:microsoft:office_2024:-::::ltsc:-:x64:
	cpe:2.3:a:microsoft:office_2024:-::::ltsc:-:x86:
	cpe:2.3:a:microsoft:office_2024:-::::ltsc:macos:-:

No data.

Vendor Product Versions

Microsoft

365 Apps

Version	Status	Scheme	Platform
`[16.0.1,16.0.20326.20138)`	affected	generic	['32-bit_systems', 'x64-based_systems']

Microsoft

Microsoft 365

Version	Status	Scheme	Platform
`—`	affected	—	['macos']

Microsoft

Office 2016

Version	Status	Scheme	Platform
`[16.0.0,16.0.5569.1000)`	affected	generic	['32-bit_systems', 'x64-based_systems']

Microsoft

Office 2019

Version	Status	Scheme	Platform
`[19.0.0,16.0.10417.20207)`	affected	generic	['32-bit_systems', 'x64-based_systems']

Microsoft

Office 2021

Version	Status	Scheme	Platform
`[16.0.1,16.0.14334.20906)`	affected	generic	['32-bit_systems', 'x64-based_systems']

Microsoft

Office 2024

Version	Status	Scheme	Platform
`[16.0.0,16.0.17932.20976)`	affected	generic	['32-bit_systems', 'x64-based_systems']

Microsoft

Office 365

Version	Status	Scheme	Platform
`[0,*]`	affected	generic	—

Microsoft

Office Macos 2021

Version	Status	Scheme	Platform
`[0,*]`	affected	generic	—

Microsoft

Office Macos 2024

Version	Status	Scheme	Platform
`[0,*]`	affected	generic	—

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

No advisories available

Metrics

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.373% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact total

References

Link	Providers
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78510

History

Sep 25, 2026 9:30 PM Description updated. Title updated. Scoring metrics updated View changes

Type	Values Removed	Values Added
Description	A remote code execution vulnerability exists when Microsoft Office improperly validates input before loading dynamic link library (DLL) files. An attacker who successfully exploited this vulnerability could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. To exploit the vulnerability, an attacker must first convince a user to open a specially crafted Office document. The updates address the vulnerability by correcting how Office validates input before loading DLL files.	Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
Title	Microsoft Office Remote Code Execution Vulnerability	Microsoft Outlook and Word Remote Code Execution Vulnerability
Metrics	cvssV3_1 `{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C'}`	cvssV3_1 `{'score': 8.4, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C'}`

Sep 24, 2026 5:30 PM Description updated. Title updated View changes

Type	Values Removed	Values Added
Description	Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code over a network.	A remote code execution vulnerability exists when Microsoft Office improperly validates input before loading dynamic link library (DLL) files. An attacker who successfully exploited this vulnerability could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. To exploit the vulnerability, an attacker must first convince a user to open a specially crafted Office document. The updates address the vulnerability by correcting how Office validates input before loading DLL files.
Title	Microsoft Outlook and Word Remote Code Execution Vulnerability	Microsoft Office Remote Code Execution Vulnerability

Sep 21, 2026 4:30 PM Description updated. Title updated View changes

Type	Values Removed	Values Added
Description	Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.	Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code over a network.
Title	Microsoft Word Remote Code Execution Vulnerability	Microsoft Outlook and Word Remote Code Execution Vulnerability

Sep 9, 2026 10:30 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}`

Sep 8, 2026 9:00 PM First appearance in the feed. Affected versions updated. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Microsoft microsoft 365
CPEs		cpe:2.3:a:microsoft:365_apps:-::::enterprise::x64:* cpe:2.3:a:microsoft:365_apps:-::::enterprise::x86:* cpe:2.3:a:microsoft:microsoft_365:-:::::macos:: cpe:2.3:a:microsoft:office_2016:-::::-::x64:* cpe:2.3:a:microsoft:office_2016:-::::-::x86:* cpe:2.3:a:microsoft:office_2019:-::::::x64: cpe:2.3:a:microsoft:office_2019:-::::::x86: cpe:2.3:a:microsoft:office_2021:-::::ltsc:-:x64: cpe:2.3:a:microsoft:office_2021:-::::ltsc:-:x86: cpe:2.3:a:microsoft:office_2021:-::::ltsc:macos:-: cpe:2.3:a:microsoft:office_2024:-::::ltsc:-:x64: cpe:2.3:a:microsoft:office_2024:-::::ltsc:-:x86: cpe:2.3:a:microsoft:office_2024:-::::ltsc:macos:-:
Vendors & Products		Microsoft microsoft 365

Sep 8, 2026 5:30 PM Description updated. Title updated. First appearance in the feed. Weaknesses updated. Affected versions updated. Affected vendors updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Description		Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.
Title		Microsoft Word Remote Code Execution Vulnerability
First Time appeared		Microsoft Microsoft 365 Apps Microsoft office 2016 Microsoft office 2019 Microsoft office 2021 Microsoft office 2024 Microsoft office 365 Microsoft office Macos 2021 Microsoft office Macos 2024
Weaknesses		CWE-122
CPEs		cpe:2.3:a:microsoft:365_apps:::::enterprise:::* cpe:2.3:a:microsoft:office_2016:::::::x86:* cpe:2.3:a:microsoft:office_2019:::::::: cpe:2.3:a:microsoft:office_2021:::::long_term_servicing_channel:::* cpe:2.3:a:microsoft:office_2024:::::long_term_servicing_channel:::* cpe:2.3:a:microsoft:office_365::::::macos::* cpe:2.3:a:microsoft:office_macos_2021::::::long_term_servicing_channel::* cpe:2.3:a:microsoft:office_macos_2024::::::long_term_servicing_channel::*
Vendors & Products		Microsoft Microsoft 365 Apps Microsoft office 2016 Microsoft office 2019 Microsoft office 2021 Microsoft office 2024 Microsoft office 365 Microsoft office Macos 2021 Microsoft office Macos 2024
References		https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78510
Metrics		cvssV3_1 `{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C'}`