Microsoft Office Excel: Heap-based buffer overflow allows remote code execution
Summary
A heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. Exploitation requires that a user opens or otherwise engages with a crafted spreadsheet, for example one received by email or download. CISA SSVC rates the issue as not automatable, and no exploitation is known at publication. CVSS 8.8 (High).
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 before the build listed at aka.ms/OfficeSecurityReleases
- Office 365 for Mac: 1.0.0 before 16.115.26110837
- Office LTSC 2021: 16.0.1 before 16.0.14334.21048
- Office LTSC 2024: 16.0.0 before 16.0.17932.21140
- Office LTSC for Mac 2021 and 2024: before 16.115.26110837
- Office Online Server: 16.0.0.0 before 16.0.10417.20236 (scope not confirmed, to be checked against MSRC)
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown (see MSRC)
- Office LTSC 2021: 16.0.14334.21048
- Office LTSC 2024: 16.0.17932.21140
- Office 365 for Mac and LTSC for Mac: 16.115.26110837
- Office Online Server: 16.0.10417.20236 (not confirmed)
Workaround
Unknown. No vendor-documented workaround found. Keep Protected View and file blocking enabled for files from the internet and email.
Exploitation
- Exploited in the wild: no evidence found.
- Public proof of concept: none found.
- Microsoft temporal score: Exploit Code Maturity 'Unproven'.
- CISA SSVC: not automatable.
Our recommendation
- Install the November 2026 security updates on all Office and Microsoft 365 installations, including Office Online Server if used.
- Prioritise systems that regularly open external spreadsheets.
- Verify the exact fixed builds on the MSRC page.
- Monitor CISA KEV and MSRC for changes.
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 msrc.microsoft.com
- CVE.org record CVE-2026-116927 www.cve.org
- Strix CVE-2026-116927 (unverified) www.strix.ai
- Qualys Patch Tuesday review November 2026 blog.qualys.com
- Stefan Gossner SharePoint security fixes November 2026 blog.stefan-gossner.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, 22:36.
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.