Microsoft Office Excel: Remote code execution via stack-based buffer overflow
Summary
A stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. The attack requires a user to open a malicious workbook, typically delivered by email or download. The CVSS score is 8.8 (High), and the CNA record describes high impact on confidentiality, integrity and availability.
Affected
- Microsoft 365 Apps for Enterprise (16.0.1 up to the fixed build; exact fixed build not confirmed in the record reviewed)
- Office 365 for Mac (1.0.0 up to 16.115.26110837)
- Office LTSC 2021 (16.0.1 up to 16.0.14334.21048)
- Office LTSC 2024 (16.0.0 up to 16.0.17932.21140 according to a secondary source, not yet verified with MSRC)
- Office LTSC for Mac 2021 and 2024 (16.0.1 and 16.0.0 up to 16.115.26110837)
- Office Online Server (16.0.0.0 up to 16.0.10417.20236 according to a secondary source, not yet verified; possibly affected)
Fixed in
- Microsoft 365 Apps for Enterprise: via the Office security release page https://aka.ms/OfficeSecurityReleases (exact build unknown)
- Office 365 for Mac and Office LTSC for Mac: 16.115.26110837 or later
- Office LTSC 2021: 16.0.14334.21048 or later
- Office LTSC 2024: unverified, possibly 16.0.17932.21140 or later
- Office Online Server: unverified, possibly 16.0.10417.20236 or later
Workaround
Unknown. No vendor-stated workaround was found.
Exploitation
- No evidence of active exploitation in the sources reviewed.
- The CISA SSVC assessment lists exploitation as none and automatable as no.
- Public proof-of-concept code: unknown.
Our recommendation
- Install the November 2026 Microsoft security update on all affected Office and Microsoft 365 installations, with priority for finance and mail-facing workstations.
- Confirm the fixed builds for each product on the MSRC advisory before relying on version checks.
- Check whether SharePoint or Office Online Server is in use and treat them as potentially affected until Microsoft confirms.
- Keep Protected View enabled for files from the internet and email, and keep automatic updates active.
- Monitor for an NVD analysis, a CISA KEV listing or a public proof of concept.
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 Update Guide: CVE-2026-118295 msrc.microsoft.com
- CVE.org CVE Record CVE-2026-118295 www.cve.org
- Strix: CVE-2026-118295 (secondary, verify) www.strix.ai
- ThreatInt: CVE-2026-118295 (secondary, verify) cve.threatint.com
- Stefan Gossner: SharePoint security fixes November 2026 blog.stefan-gossner.com
- Tenable: Microsoft November 2026 Patch Tuesday www.tenable.com
- NT Compatible: Microsoft November 2026 Patch Tuesday www.ntcompatible.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, 22:08.
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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