Microsoft Office Excel: Remote code execution via stack-based buffer overflow
Summary
A stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. The attacker needs no privileges, but a user must take an action, typically opening a crafted Excel file received by email or shared over a file share. Successful exploitation can lead to full compromise of the affected user's system.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 before the fixed build (see Microsoft advisory)
- 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: 16.0.x before 16.115.26110837
- Office Online Server: 16.0.0.0 before 16.0.10417.20236
Fixed in
- Microsoft 365 Apps for Enterprise: Fixed build not stated in the sources; use aka.ms/OfficeSecurityReleases
- Office 365 for Mac and LTSC for Mac: 16.115.26110837
- Office LTSC 2021: 16.0.14334.21048
- Office LTSC 2024: 16.0.17932.21140 (secondary source, verify at MSRC)
- Office Online Server: 16.0.10417.20236 (secondary source, verify at MSRC)
Workaround
Unknown. No vendor-documented workaround found; apply the security update. Keep Protected View and attachment blocking enabled as general good practice.
Exploitation
- No exploitation in the wild reported; no public proof of concept found.
- CISA SSVC: Exploitation none, Automatable no, Technical impact total.
- Exploit code maturity: Unproven (E:U).
Our recommendation
- Apply the Microsoft November 2026 security update to all affected Office installations, prioritising Office Online Server if it is internet-exposed.
- Verify fixed builds in the MSRC advisory before rollout.
- Check whether Office Online Server is deployed.
- Warn users not to open Excel files from unknown senders and monitor for suspicious Excel activity.
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 Update Guide: CVE-2026-118704 msrc.microsoft.com
- CVE Record CVE-2026-118704 www.cve.org
- Strix AI: CVE-2026-118704 www.strix.ai
- ThreatInt: CVE-2026-118704 cve.threatint.com
- BleepingComputer: Microsoft November 2026 Patch Tuesday www.bleepingcomputer.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, 21:55.
Original description (NVD)
Stack-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.