Microsoft Office Excel: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. Exploitation requires a user to open a crafted spreadsheet, typically received by email or download. The CVSS v3.1 base score is 8.8 (High), and Microsoft has published fixes with its November 2026 Patch Tuesday.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (exact build to be confirmed in the MSRC advisory)
- Microsoft Office 365 for Mac: 1.0.0 to before 16.115.26110837
- Microsoft Office LTSC 2021: 16.0.1 to before 16.0.14334.21048
- Microsoft Office LTSC 2024: 16.0.0 to before 16.0.17932.21140 (unverified third-party data)
- Microsoft Office LTSC for Mac 2021 and 2024: before 16.115.26110837 (unverified third-party data)
- Microsoft Office Online Server: 16.0.0.0 to before 16.0.10417.20236 (unverified third-party data)
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown, see https://aka.ms/OfficeSecurityReleases
- Microsoft Office 365 for Mac: 16.115.26110837
- Microsoft Office LTSC 2021: 16.0.14334.21048
- Microsoft Office LTSC 2024: 16.0.17932.21140 (unverified, confirm with MSRC)
- Microsoft Office LTSC for Mac 2021 and 2024: 16.115.26110837 (unverified, confirm with MSRC)
- Microsoft Office Online Server: 16.0.10417.20236 (unverified, confirm with MSRC)
Workaround
Unknown. No vendor workaround was identified beyond installing the patch.
Exploitation
No exploitation in the wild or public proof of concept was found at the time of writing. The CVE record lists Exploit Code Maturity as Unproven (E:U). CISA KEV status has not been checked.
Our recommendation
- Install the November 2026 Office updates on all Microsoft 365 and LTSC clients, then verify build numbers against the MSRC table.
- Keep Protected View enabled for files from the internet and email, and restrict macros from untrusted sources.
- Monitor for exploitation reports and recheck CISA KEV and NVD once the NVD analysis is complete.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Remote code execution – Microsoft Office Excel
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Microsoft Office
- Updates (KB)
- KB5002946
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Response Center advisory CVE-2026-124174 msrc.microsoft.com
- CVE Record CVE-2026-124174 www.cve.org
- Strix CVE-2026-124174 (third-party, unverified builds) www.strix.ai
- VulDB Excel vulnerability (product context) vuldb.com
- Cybersecurity News: Microsoft November 2026 Patch Tuesday cybersecuritynews.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 10 Nov 2026, 21:11.
Original description (NVD)
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.