Microsoft Office Excel: Remote code execution via heap-based buffer overflow
Summary
Microsoft Office Excel contains a heap-based buffer overflow that allows a remote attacker without privileges to execute code. The CVSS vector requires user interaction, for example opening a crafted spreadsheet from an e-mail or download. The CNA rates it 8.8 (High), while VulDB rates it 6.3 (Medium).
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (exact build unconfirmed)
- Office 365 for Mac: before 16.115.26110837
- Office LTSC 2021: before 16.0.14334.21048
- Office LTSC 2024: before 16.0.17932.21140
- Office LTSC for Mac 2021: before 16.115.26110837
- Office LTSC for Mac 2024: before 16.115.26110837
- Office Online Server: before 16.0.10417.20236
Versions are taken from the CNA record and must be confirmed in the MSRC advisory.
Fixed in
Unknown. The MSRC advisory could not be checked, so fixed build numbers are not confirmed. Microsoft 365 is updated via the release notes at https://aka.ms/OfficeSecurityReleases
Workaround
Unknown. No vendor workaround was found. General hardening, not confirmed for this CVE:
- Block or sandbox untrusted attachments from the internet.
- Keep Protected View enabled for files from the internet.
Exploitation
No evidence of exploitation found. The CVE is not listed in the CISA KEV alerts checked, but this is not a confirmed absence. VulDB states that no exploit is available. A broker price estimate of USD 5k–25k exists, which is not evidence of a sale. CISA SSVC: exploitation none, automatable no, technical impact total.
Our recommendation
- Patch Microsoft 365 Apps and Office LTSC clients through the normal update channel once the MSRC fixed builds are confirmed.
- Prioritise users who open external spreadsheets.
- Remind staff not to open unexpected spreadsheets from e-mail or downloads.
- Check the MSRC advisory and the CISA KEV catalog for updates.
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.org record CVE-2026-118714 www.cve.org
- Microsoft Security Update Guide msrc.microsoft.com
- VulDB entry 434124 vuldb.com
- Strix AI CVE mirror www.strix.ai
- ThreatInt CVE mirror cve.threatint.com
- CISA KEV alert 2026-10-29 www.cisa.gov
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, 21:55.
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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