Microsoft Excel: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Excel, part of Microsoft 365 Apps and Office LTSC releases, allows an unauthorized attacker to execute code over the network. According to the CVSS vector, exploitation requires a user to open a malicious Excel file, for example from an email attachment or download. Successful exploitation would give code execution in the user's context. No exploitation is known at publication.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (exact build unknown)
- 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: 16.0.1 before 16.115.26110837
- Office LTSC for Mac 2024: 16.0.0 before 16.115.26110837
- Office Online Server: 16.0.0.0 before 16.0.10417.20236
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown. Check the Microsoft Office security release notes.
- Office 365 for Mac and Office LTSC for Mac 2021/2024: 16.115.26110837
- Office LTSC 2021: 16.0.14334.21048
- Office LTSC 2024: 16.0.17932.21140
- Office Online Server: 16.0.10417.20236
Workaround
- Unknown. No vendor workaround was found in the available sources. Check the MSRC advisory.
- Until patched, block or quarantine Excel files from untrusted senders and keep Protected View enabled for internet-sourced files (general practice, not from a source).
Exploitation
- No known exploitation at publication. The CVSS exploit code maturity is 'unproven'.
- No public PoC, CISA KEV listing or in-the-wild reports found. NVD analysis is pending.
Our recommendation
- Patch Microsoft 365 and Office LTSC clients promptly.
- Prioritise any Office Online Server instance, especially if it is reachable from the internet.
- Review email filtering for Excel attachments.
- Check the sibling CVEs CVE-2026-120791 and CVE-2026-120788 in the same patch cycle.
- Monitor CISA KEV and the MSRC page 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
- CVE Record CVE-2026-120790 (CVE.org) www.cve.org
- Microsoft Security Update Guide CVE-2026-120790 msrc.microsoft.com
- Strix CVE-2026-120790 (third-party mirror) www.strix.ai
- Strix CVE-2026-120791 (related Excel CVE) www.strix.ai
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, 21:28.
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.
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