Microsoft Office Excel: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Excel allows an unauthorized attacker to execute code over a network. The CVSS base score is 8.8 (High), and Microsoft rates the issue Important. Exploitation requires a user to open a crafted spreadsheet, for example one delivered by phishing or a download.
Affected
- Microsoft 365 Apps for Enterprise (32-bit and x64): builds from 16.0.1 before the fix (fixed build unknown)
- Office 365 for Mac: 1.0.0 before 16.115.26110837
- Office LTSC 2021 (32-bit and x64): 16.0.1 before 16.0.14334.21048
- Office LTSC 2024: 16.0.0 before 16.0.17932.21140 (unverified, from secondary sources)
- Office LTSC for Mac 2021 and 2024: 16.0.1 / 16.0.0 before 16.115.26110837
- Office Online Server: 16.0.0.0 before 16.0.10417.20236 (unverified, from secondary sources)
Fixed in
- Fixed in the Microsoft November 2026 Office security updates (Patch Tuesday). Exact fixed builds: see the vendor advisory; the thresholds above are the first fixed builds per the CNA record, except where marked as unverified.
Workaround
- Unknown. No workarounds were documented in the sources reviewed.
Exploitation
- No evidence of exploitation in the wild, public proof of concept or CISA KEV listing was found at the time of review. CISA SSVC: exploitation none, automatable no, technical impact total.
Our recommendation
- Deploy the November 2026 Office security updates on all Microsoft 365, Office 365 for Mac, Office LTSC and Office Online Server systems with priority.
- Verify installed build numbers against the thresholds above, and check Office LTSC and Office Online Server separately.
- Until patched, block or quarantine spreadsheet attachments from unknown senders and do not open untrusted files.
- Restrict user privileges to limit the impact of code execution.
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
- CVE Record (CNA) www.cve.org
- Microsoft Security Update Guide msrc.microsoft.com
- BleepingComputer: Microsoft November 2026 Patch Tuesday www.bleepingcomputer.com
- Cybersecurity News: Microsoft November 2026 Patch Tuesday cybersecuritynews.com
- threatint CVE-2026-118722 cve.threatint.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, 21:44.
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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