Microsoft Office Excel: Remote Code Execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Office Excel allows an unauthenticated attacker to execute code over a network. Exploitation requires that a user opens a crafted Excel file, for example one received by email or downloaded from the internet. Successful exploitation would give the attacker code execution with the rights of the user.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build listed on MSRC (the CVE record link is malformed)
- Microsoft 365 Apps for Mac and Office LTSC for Mac 2021/2024: versions below 16.114.26101123 per CVE record
- Office LTSC 2021: versions below 16.0.14334.20974 per CVE record
- Office LTSC 2024: versions below 16.0.17932.21056 per CVE record
- Office Online Server: versions below 16.0.10417.20228
Fixed in
- Office Online Server: 16.0.10417.20228 (security update KB5002928, October 13, 2026)
- Other products: fixed builds are not confirmed in our sources. Check the MSRC Security Update Guide for each Office channel in use.
Workaround
- No vendor workaround found. Install the security update instead.
- General hardening (not from a vendor source): keep Protected View enabled and block macros from the internet. Verify before relying on these for this CVE.
Exploitation
- CISA SSVC data in the CVE record: Exploitation none, Automatable no, Technical Impact total.
- No public proof-of-concept or in-the-wild exploitation was found in our research.
- CISA KEV status was not verified.
Our recommendation
- Install the October 2026 cumulative updates for all Microsoft 365 and Office installations, and check the fixed build on MSRC for each channel.
- Check the Mac and Office Online Server builds separately.
- Filter or sandbox spreadsheet attachments at the mail gateway and train users not to open unexpected Excel files.
- Monitor for unusual Excel child processes and verify the KEV status before the next review.
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-2026-97754 msrc.microsoft.com
- Microsoft Support: KB5002928 Office Online Server security update support.microsoft.com
- Microsoft 365 Apps security updates learn.microsoft.com
- Release notes for Office for Mac learn.microsoft.com
- OpenCVE: CVE-2026-97754 app.opencve.io
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, 17:40.
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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