Integer underflow in Microsoft Office Excel allows remote code execution
Priority MEDIUM 42CWE-122Published · 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-122 and the CVSS impact.
Summary
Microsoft Office Excel in Microsoft 365 Apps for Enterprise, Office 365 for Mac, Office LTSC 2021, Office LTSC 2024, Office LTSC for Mac 2021 and 2024, and Office Online Server is affected. An integer underflow (CWE-191) lets Excel miscalculate a value and write memory out of bounds. An unauthorized attacker can execute code over a network, but a user must take an action for the attack to succeed.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
Description from the CNA
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0082 57th percentileScored 2026-11-07
Fix Fixed Microsoft 365 Apps for Enterprise (Microsoft): https://aka.ms/OfficeSecurityReleasesMicrosoft Office 365 for Mac (Microsoft): 16.114.26101123+5 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 | Office Online Server | 16.0.0.0 to before 16.0.10417.20228 | 16.0.10417.20228 | 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
- Office Online Server VendorMicrosoft Affected 16.0.0.0 to before 16.0.10417.20228 Fixed in 16.0.10417.20228 Patch available CNA
CPE configurations NVD · 10
| 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:office_online_server:*:*:*:*:*:*:*:* | before 16.0.10417.20228 | 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
- cpe:2.3:a:microsoft:office_online_server:*:*:*:*:*:*:*:* Versions before 16.0.10417.20228 Vulnerable ·Microsoft
Remediation
Update Microsoft 365 Apps for Enterprise to the release listed at aka.ms/OfficeSecurityReleases. Update Office 365 for Mac and Office LTSC for Mac 2021 and 2024 to 16.114.26101123, Office LTSC 2021 to 16.0.14334.20974, Office LTSC 2024 to 16.0.17932.21056, and Office Online Server to 16.0.10417.20228.
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
- Fix · CNA Office Online Server (Microsoft) Fixed in 16.0.10417.20228
Timeline
- 2026-10-13 Threatist record created from CVE-2026-97739
- 2026-10-13 Alias added: GHSA-g8vq-mrq5-m545
- 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-2026-97739 · CVE Program
- CVE-2026-97739 · NVD
- FIRST EPSS
- GHSA-g8vq-mrq5-m545 · 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