Microsoft Office Excel: Remote code execution via heap-based buffer overflow
Summary
A heap-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 manipulated file, for example an email attachment or a download. Successful exploitation would give the attacker full control over confidentiality, integrity and availability on the affected computer.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 before the fixed build (see Microsoft release page)
- Microsoft Office 365 for Mac: 1.0.0 before 16.114.26101123
- Microsoft Office LTSC 2021: 16.0.1 before 16.0.14334.20974
- Microsoft Office LTSC 2024: 16.0.0 before 16.0.17932.21056
- Microsoft Office LTSC for Mac 2021: 16.0.1 before 16.114.26101123
- Microsoft Office LTSC for Mac 2024: 16.0.0 before 16.114.26101123
- Microsoft Office Online Server: 16.0.0.0 before 16.0.10417.20228
Fixed in
- Office LTSC 2021: 16.0.14334.20974 (reported by secondary source, verify on MSRC)
- Office LTSC 2024: 16.0.17932.21056 (reported by secondary source, verify on MSRC)
- Office for Mac and LTSC for Mac: 16.114.26101123 (reported by secondary source, verify on MSRC)
- Office Online Server: 16.0.10417.20228 (reported by secondary source, verify on MSRC)
- Microsoft 365 Apps for Enterprise: Unknown per channel, check the Microsoft release page
Workaround
- No Microsoft-documented workaround found.
- Third-party recommendation (OpenCVE, not in Microsoft's advisory): disable automatic macro execution and set trusted document settings to prompt on file open.
- Keep Protected View enabled for files from untrusted sources.
Exploitation
- Microsoft: not publicly disclosed.
- CISA SSVC data: exploitation none, automatable no.
- Not listed in CISA KEV at the time of research.
- No public proof of concept or confirmed in-the-wild exploitation found.
Our recommendation
- Install the October 2026 Microsoft security update for Office on all affected systems, prioritising systems that process external spreadsheets, invoices or attachments.
- Check the MSRC page for the exact fixed build of your Microsoft 365 channel.
- Apply the workaround settings if patching is delayed.
- Verify that LTSC 2021 installations are still supported; reports state support ended on 13 October 2026, and migration may be needed.
- Monitor email gateways for suspicious spreadsheet attachments.
Information from Microsoft (Patch Tuesday October 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)
- KB5002928
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-97768 msrc.microsoft.com
- OpenCVE: CVE-2026-97768 app.opencve.io
- Vulners CVE record: CVE-2026-97768 vulners.com
- Microsoft 365 Apps security updates learn.microsoft.com
- Strix.ai: CVE-2026-97768 www.strix.ai
- Office Watch: October 2026 Patch Tuesday Office critical fixes office-watch.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 31 Oct 2026, 17:26.
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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