Microsoft Office Excel: Stack-based buffer overflow allows remote code execution
Summary
A stack-based buffer overflow in Microsoft Excel, part of Microsoft Office, can be exploited by an unauthorized attacker over a network. Exploitation requires a user to open a crafted file, which makes email and file sharing the most likely attack paths. A successful attack could lead to code execution with high impact on confidentiality, integrity and availability. Microsoft rates the flaw as Critical in some release notes, while the CVSS base score is 8.8 (High).
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build listed at aka.ms/OfficeSecurityReleases (exact build unknown)
- Office 365 for Mac: 1.0.0 to before 16.115.26110837
- Office LTSC 2021: 16.0.1 to before 16.0.14334.21048
- Office LTSC 2024: 16.0.0 to before 16.0.17932.21140
- Office LTSC for Mac 2021 and 2024: 16.0.1 / 16.0.0 to before 16.115.26110837
- Office Online Server: 16.0.0.0 to before 16.0.10417.20236
Fixed in
- Microsoft 365 Apps for Enterprise: November 2026 Office updates (exact build unknown, see aka.ms/OfficeSecurityReleases)
- Office 365 for Mac and LTSC for Mac: 16.115.26110837 or later
- Office LTSC 2021: 16.0.14334.21048 or later
- Office LTSC 2024: 16.0.17932.21140 or later
- Office Online Server: 16.0.10417.20236 or later
Workaround
- No official workaround known. Install the fix.
- Keep Protected View enabled and do not open spreadsheets from unknown senders until patched.
Exploitation
- Exploited in the wild: No evidence found at the time of writing.
- Public proof of concept: None found.
- CISA SSVC: Exploitation none, automatable no, technical impact total.
- CVSS exploit maturity: Unproven (E:U).
Our recommendation
- Patch all Microsoft 365 and LTSC Office clients in the next update cycle and treat this as high priority.
- Check separately whether Office Online Server is deployed and patch it.
- Confirm the exact fixed build numbers on the MSRC advisory.
- Warn staff not to open unexpected Excel files from unknown senders until patched.
- Monitor for exploitation news and update the tracker if the status changes.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Critical
- 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
- MSRC Security Update Guide msrc.microsoft.com
- CVE Record (CVE.org) www.cve.org
- Strix CVE-2026-118292 www.strix.ai
- Microsoft November 2026 Patch Tuesday (Cybersecuritynews) cybersecuritynews.com
- SharePoint security fixes November 2026 (Gossner) blog.stefan-gossner.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, 22:06.
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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