Microsoft Office Excel: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Excel, part of the Office suite, allows an unauthenticated remote attacker to execute code. Per the CVSS vector, the attack needs no privileges but requires a user to interact, for example by opening a crafted file received by email or via file sharing. The affected builds differ per Office edition, including Microsoft 365 Apps, LTSC releases and Mac versions, and Office Online Server may also be affected.
Affected
- Microsoft 365 Apps for Enterprise (Windows): 16.0.1 before the fixed build referenced at https://aka.ms/OfficeSecurityReleases (exact build not stated in the record)
- Microsoft Office 365 for Mac: 1.0.0 before 16.115.26110837
- Microsoft Office LTSC 2021: 16.0.1 before 16.0.14334.21048
- Microsoft Office LTSC 2024: 16.0.0 before 16.0.17932.21140 (unverified, from third-party aggregator)
- Microsoft Office LTSC for Mac 2021 and 2024: versions before 16.115.26110837 (unverified)
- Microsoft Office Online Server: 16.0.0.0 before 16.0.10417.20236 (unverified)
Fixed in
- Security updates from Microsoft for the November 2026 Office release. Verify exact build numbers at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-118701 before rollout.
- 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 (unverified)
Workaround
Unknown.
Exploitation
- No evidence of exploitation in the wild found; not checked against CISA KEV.
- CISA SSVC assessment: exploitation none, not automatable, total technical impact.
- No public proof of concept found at the time of research.
Our recommendation
- Apply the November 2026 Office security updates to all Excel clients, starting with exposed mail and file-sharing workflows.
- Verify Office Online Server builds if you run it.
- Confirm build numbers against the MSRC advisory before rollout.
- Train users not to open unexpected Excel files from unknown senders.
- Monitor for unusual Excel process activity and recheck KEV 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 (MSRC) msrc.microsoft.com
- CVE.org CVE Record www.cve.org
- VulDB entry vuldb.com
- Stefan Gossner blog: November 2026 SharePoint PU fixes blog.stefan-gossner.com
- Strix AI CVE-2026-118701 www.strix.ai
- threatint CVE-2026-118701 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, 22:01.
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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