Microsoft Office Excel: Stack-based buffer overflow leading to remote code execution
Summary
A stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. Exploitation requires that a user opens a malicious file or otherwise triggers the flaw, for example through a document received by email. The CVSS 3.1 base score is 8.8 (High), and the record reports no known exploit code at publication.
Affected
- Microsoft 365 Apps for Enterprise: from 16.0.1 before the build listed on Microsoft's Office security release page (exact build unknown)
- Office LTSC 2021: from 16.0.1 before 16.0.14334.21048
- Office LTSC 2024: from 16.0.0 before 16.0.17932.21140
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown (check MSRC and aka.ms/OfficeSecurityReleases)
- Office LTSC 2021: 16.0.14334.21048
- Office LTSC 2024: 16.0.17932.21140
Workaround
Unknown.
Exploitation
- Known exploitation in the wild: No evidence found; not verified against the CISA KEV catalog
- Public proof-of-concept exploit: None found
- Microsoft exploit maturity (CVSS E:U): Unproven
Our recommendation
- Install the Microsoft Office security update for your version as a priority, starting with Microsoft 365 Apps and LTSC 2021/2024 builds listed above
- Verify the fixed build for Microsoft 365 Apps on MSRC before relying on it
- Restrict opening spreadsheets from unknown senders and keep Protected View enabled for files from the internet
- Check the CISA KEV catalog and the NVD analysis once available, and reassess priority
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide: CVE-2026-123385 msrc.microsoft.com
- CVE.org CVE Record: CVE-2026-123385 www.cve.org
- Strix AI mirror: CVE-2026-123385 www.strix.ai
- CISA Known Exploited Vulnerabilities Catalog www.cisa.gov
- Proofpoint: 2026 vulnerability exploitation via email-weaponised documents www.proofpoint.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, 21:12.
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.
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