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. The attack requires that a user opens a crafted file, for example an email attachment or a shared spreadsheet. Microsoft 365 Apps, Office LTSC, Office for Mac and Office Online Server are listed as affected in the CVE record.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 to before the build listed on Microsoft's release page
- 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
- Microsoft Office LTSC for Mac 2021: 16.0.1 to before 16.115.26110837
- Microsoft Office LTSC for Mac 2024: 16.0.0 to before 16.115.26110837
- Microsoft Office Online Server: 16.0.0.0 to before 16.0.10417.20236
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown (build not stated in the CVE record; see Microsoft's release page)
- Microsoft Office 365 for Mac: 16.115.26110837
- Microsoft Office LTSC 2021: 16.0.14334.21048
- Microsoft Office LTSC 2024: 16.0.17932.21140
- Microsoft Office LTSC for Mac 2021 and 2024: 16.115.26110837
- Microsoft Office Online Server: 16.0.10417.20236
Workaround
Unknown. No vendor-published workaround was identified. Keep Protected View and file-blocking settings enabled as general hardening.
Exploitation
- No evidence of exploitation in the wild found at the time of research
- No public proof of concept found
- Not listed in the CISA KEV catalogue at the time of research
- Microsoft temporal metrics: E:U (exploit code maturity Unproven)
- EPSS: Unknown
Our recommendation
- Install the latest Microsoft Office security updates on all affected clients and servers, starting with Microsoft 365 Apps and LTSC clients used for email and document handling.
- Verify installed build numbers against the MSRC advisory, because the Microsoft 365 Apps build and the full product list were not confirmed in the sources.
- Treat Excel files from unknown senders as untrusted, and keep Protected View enabled.
- Monitor the MSRC page and the CISA KEV catalogue for updates on exploitation.
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: CVE-2026-120791 (linked, not retrieved) msrc.microsoft.com
- CVE.org CNA record CVE-2026-120791 www.cve.org
- Strix aggregator CVE-2026-120791 (third-party, unverified) 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, 21:31.
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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