Stack buffer overflow in Microsoft Office Word allows code execution
Priority MEDIUM 42CWE-121Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-121 and the CVSS impact.
Summary
Microsoft Office Word in Microsoft 365 Apps for Enterprise from 16.0.1, Microsoft Office 365 for Mac from 1.0.0 before 16.114.26101123, and several Office LTSC 2021, LTSC 2024 and LTSC for Mac releases is affected. A stack-based buffer overflow (CWE-121) lets an unauthorized attacker execute code over a network. The attack requires user interaction.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
Description from the CNA
Stack-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00901 59th percentileScored 2026-11-07
Fix Fixed Microsoft 365 Apps for Enterprise (Microsoft): https://aka.ms/OfficeSecurityReleasesMicrosoft Office 365 for Mac (Microsoft): 16.114.26101123+4 more products
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Microsoft | Microsoft 365 Apps for Enterprise | 16.0.1 to before https://aka.ms/OfficeSecurityReleases | https://aka.ms/OfficeSecurityReleases | Patch available | CNA |
| Microsoft | Microsoft Office 365 for Mac | 1.0.0 to before 16.114.26101123 | 16.114.26101123 | Patch available | CNA |
| Microsoft | Microsoft Office LTSC 2021 | 16.0.1 to before 16.0.14334.20974 | 16.0.14334.20974 | Patch available | CNA |
| Microsoft | Microsoft Office LTSC 2024 | 16.0.0 to before 16.0.17932.21056 | 16.0.17932.21056 | Patch available | CNA |
| Microsoft | Microsoft Office LTSC for Mac 2021 | 16.0.1 to before 16.114.26101123 | 16.114.26101123 | Patch available | CNA |
| Microsoft | Microsoft Office LTSC for Mac 2024 | 16.0.0 to before 16.114.26101123 | 16.114.26101123 | Patch available | CNA |
- Microsoft 365 Apps for Enterprise VendorMicrosoft Affected 16.0.1 to before https://aka.ms/OfficeSecurityReleases Fixed in https://aka.ms/OfficeSecurityReleases Patch available CNA
- Microsoft Office 365 for Mac VendorMicrosoft Affected 1.0.0 to before 16.114.26101123 Fixed in 16.114.26101123 Patch available CNA
- Microsoft Office LTSC 2021 VendorMicrosoft Affected 16.0.1 to before 16.0.14334.20974 Fixed in 16.0.14334.20974 Patch available CNA
- Microsoft Office LTSC 2024 VendorMicrosoft Affected 16.0.0 to before 16.0.17932.21056 Fixed in 16.0.17932.21056 Patch available CNA
- Microsoft Office LTSC for Mac 2021 VendorMicrosoft Affected 16.0.1 to before 16.114.26101123 Fixed in 16.114.26101123 Patch available CNA
- Microsoft Office LTSC for Mac 2024 VendorMicrosoft Affected 16.0.0 to before 16.114.26101123 Fixed in 16.114.26101123 Patch available CNA
CPE configurations NVD · 9
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:* | not specified by NVD | Vulnerable | Microsoft |
| cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x86:* | not specified by NVD | Vulnerable | Microsoft |
| cpe:2.3:a:microsoft:microsoft_365:-:*:*:*:*:macos:*:* | not specified by NVD | Vulnerable | Microsoft |
| cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x64:* | not specified by NVD | Vulnerable | Microsoft |
| cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x86:* | not specified by NVD | Vulnerable | Microsoft |
| cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:macos:-:* | not specified by NVD | Vulnerable | Microsoft |
| cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x64:* | not specified by NVD | Vulnerable | Microsoft |
| cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x86:* | not specified by NVD | Vulnerable | Microsoft |
| cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:macos:-:* | not specified by NVD | Vulnerable | Microsoft |
- cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:* Versions not specified by NVD Vulnerable ·Microsoft
- cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x86:* Versions not specified by NVD Vulnerable ·Microsoft
- cpe:2.3:a:microsoft:microsoft_365:-:*:*:*:*:macos:*:* Versions not specified by NVD Vulnerable ·Microsoft
- cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x64:* Versions not specified by NVD Vulnerable ·Microsoft
- cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x86:* Versions not specified by NVD Vulnerable ·Microsoft
- cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:macos:-:* Versions not specified by NVD Vulnerable ·Microsoft
- cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x64:* Versions not specified by NVD Vulnerable ·Microsoft
- cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x86:* Versions not specified by NVD Vulnerable ·Microsoft
- cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:macos:-:* Versions not specified by NVD Vulnerable ·Microsoft
Remediation
Update Microsoft 365 Apps for Enterprise using Microsoft's Office security releases guidance. Install version 16.114.26101123 of Microsoft Office 365 for Mac, Microsoft Office LTSC for Mac 2021 and Microsoft Office LTSC for Mac 2024. Install version 16.0.14334.20974 of Microsoft Office LTSC 2021 and version 16.0.17932.21056 of Microsoft Office LTSC 2024.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
- Fix · CNA Microsoft 365 Apps for Enterprise (Microsoft) Fixed in https://aka.ms/OfficeSecurityReleases
- Fix · CNA Microsoft Office 365 for Mac (Microsoft) Fixed in 16.114.26101123
- Fix · CNA Microsoft Office LTSC 2021 (Microsoft) Fixed in 16.0.14334.20974
- Fix · CNA Microsoft Office LTSC 2024 (Microsoft) Fixed in 16.0.17932.21056
- Fix · CNA Microsoft Office LTSC for Mac 2021 (Microsoft) Fixed in 16.114.26101123
- Fix · CNA Microsoft Office LTSC for Mac 2024 (Microsoft) Fixed in 16.114.26101123
Timeline
- 2026-10-13 Threatist record created from CVE-2026-83891
- 2026-10-13 Alias added: GHSA-cw5m-j449-89h4
- 2026-10-14 Priority changed: LOW → MEDIUM
- 2026-10-16 Fix available: Microsoft/Microsoft Office 365 for [email protected], Microsoft/Microsoft Office LTSC for Mac [email protected], Microsoft/Microsoft Office LTSC for Mac [email protected] · CNA
References
More Microsoft 365 Apps vulnerabilities
- TI-2024-14173 Microsoft Outlook Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
- TI-2023-09240 Microsoft Outlook Elevation of Privilege Vulnerability KEVCVSS 3.1CRITICAL 9.8
- TI-2024-25471 Microsoft Project Remote Code Execution Vulnerability KEVCVSS 3.1HIGH 8.8
- TI-2023-17652 Microsoft Outlook Security Feature Bypass Vulnerability KEVCVSS 3.1HIGH 8.8
- TI-2026-17368 Microsoft Word Security Feature Bypass Vulnerability KEVCVSS 3.1HIGH 7.8
- TI-2026-17363 Microsoft Office Security Feature Bypass Vulnerability KEVCVSS 3.1HIGH 7.8
Sources
- CVE-2026-83891 · CVE Program
- CVE-2026-83891 · NVD
- FIRST EPSS
- GHSA-cw5m-j449-89h4 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences