Microsoft Office Excel: Stack-based buffer overflow allows code execution
Summary
A stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network (CVSS 8.8). The attack requires a user to open a crafted file, such as an Excel attachment or download, and no privileges are needed. Successful exploitation would give the attacker full control over the affected user's system. No exploitation is known at publication.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (see aka.ms/OfficeSecurityReleases)
- 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 (secondary source, to be confirmed on MSRC)
- Office LTSC for Mac 2021 and 2024: before 16.115.26110837 (listed in the CVE record, to be confirmed)
- Office Online Server: 16.0.0.0 before 16.0.10417.20236 (listed in the CVE record, to be confirmed)
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown (fixed build referenced at aka.ms/OfficeSecurityReleases)
- Office 365 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 (to be confirmed on MSRC)
- Fixed in Microsoft's November 2026 security updates
Workaround
Unknown.
Exploitation
- CISA SSVC: Exploitation none, Automatable no, Technical Impact total
- Exploit maturity E:U (unproven) in the CVSS vector
- No in-the-wild exploitation or public proof-of-concept code known at publication
Our recommendation
- Install the November 2026 Office updates, prioritising Microsoft 365 Apps and LTSC installs
- Check Mac and perpetual LTSC installs separately, as they often need explicit deployment
- Confirm fixed builds on MSRC and aka.ms/OfficeSecurityReleases
- Remind staff not to open unexpected Excel files from unknown senders
- Re-check MSRC and CISA KEV for changes to the exploitation status
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
- Microsoft Security Update Guide: CVE-2026-118711 msrc.microsoft.com
- CVE Record CVE-2026-118711 (CNA Microsoft) www.cve.org
- Microsoft November 2026 Patch Tuesday (Cybersecurity News) cybersecuritynews.com
- Strix AI: CVE-2026-118711 www.strix.ai
- Threatint: CVE-2026-118711 cve.threatint.com
- Vulners: PT-2026-118711 vulners.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, 21:53.
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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