Microsoft Office Excel: Heap-based buffer overflow enables remote code execution
Summary
A heap-based buffer overflow in Microsoft Office Excel allows a remote attacker to execute code on the affected system. Exploitation requires that a user opens or processes a malicious Excel file, for example one received by email or downloaded from the internet. No privileges or authentication are needed, and CVSS rates the issue 8.8 (high). No exploitation in the wild is documented in the sources reviewed.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build listed by Microsoft (exact build unknown)
- Office 365 for Mac: before 16.115.26110837
- Office LTSC 2021: before 16.0.14334.21048
- Office LTSC 2024: before 16.0.17932.21140 (secondary source, not verified against MSRC)
- Office LTSC for Mac 2021 and 2024: before 16.115.26110837 (secondary source, not verified)
- Office Online Server: before 16.0.10417.20236 (secondary source, not verified)
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown (see MSRC advisory)
- 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 verified)
- Office LTSC for Mac 2021 and 2024: 16.115.26110837 or later (to be verified)
- Office Online Server: 16.0.10417.20236 or later (to be verified)
Workaround
Unknown. No vendor workaround is documented in the sources reviewed.
- Keep Protected View enabled for files from the internet and email until patched.
- Block or quarantine untrusted Excel attachments at the mail gateway.
- Restrict macro and add-in use where possible.
Exploitation
- No exploitation in the wild is confirmed in the sources reviewed.
- No CISA KEV entry or public proof of concept was found.
- CISA SSVC assessment: exploitation none, not automatable, total technical impact.
- VulDB reports a broker-market price estimate of USD 5k to 25k. This is not evidence of exploitation.
Our recommendation
- Check the MSRC advisory for the authoritative build list and patch all affected Office installations promptly.
- Verify installed builds in the Microsoft 365 admin centre or on each device.
- Keep Protected View enabled and filter or quarantine untrusted Excel attachments until patched.
- Restrict macros and add-ins where possible.
- Monitor for unusual Excel child processes and prioritise users who handle email attachments.
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 (MSRC) msrc.microsoft.com
- CVE.org CNA record (Microsoft) www.cve.org
- VulDB CVE-2026-118705 vuldb.com
- Strix CVE-2026-118705 www.strix.ai
- threatint CVE-2026-118705 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, 21:56.
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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