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 that a user opens a crafted Excel file, for example an email attachment or a downloaded document. The attacker needs no privileges, and a successful attack can impact confidentiality, integrity and availability of the affected system.
Affected
- Microsoft 365 Apps for Enterprise (32-bit and x64): from 16.0.1 before the fixed build named in Microsoft's security release page
- Microsoft Office 365 for Mac: from 1.0.0 before 16.115.26110837
- Office LTSC 2021 (32-bit and x64): from 16.0.1 before 16.0.14334.21048
- Office LTSC 2024 (32-bit and x64): affected, fixed build not confirmed in the primary CVE record
- Office LTSC for Mac 2021 and 2024, Office Online Server: listed by a secondary aggregator only, not confirmed by the CVE record
Fixed in
- Office LTSC 2021: 16.0.14334.21048
- Office 365 for Mac: 16.115.26110837
- Office LTSC 2024: unconfirmed; an aggregator lists 16.0.17932.21140
- Microsoft 365 Apps for Enterprise: Unknown, check MSRC
- Office LTSC for Mac and Office Online Server: aggregator lists 16.115.26110837 and 16.0.10417.20236, unconfirmed
Workaround
Unknown.
Exploitation
- No evidence of exploitation in the wild found; CVSS exploit maturity is E:U (Unproven)
- CISA KEV not checked
- No public proof of concept found
- Published on 2026-11-10, so little time for public analysis
Our recommendation
- Install the Microsoft security updates for Office clients in the next regular update cycle and verify the fixed builds on MSRC before rollout
- Check whether Office LTSC 2024, Office Online Server and Mac builds are present and affected
- Keep Protected View and attachment-blocking policies enabled and restrict macros and external content for files received from outside the organisation
- Monitor NVD (analysis pending) and CISA KEV 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 unlikely
- 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-2026-120785 msrc.microsoft.com
- CVE Record CVE-2026-120785 www.cve.org
- Strix CVE summary CVE-2026-120785 www.strix.ai
- VulDB entry 434115 (Excel product classification) vuldb.com
- Microsoft November 2026 Patch Tuesday overview 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, 21:31.
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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