Microsoft Office Excel: Heap-based buffer overflow allows remote code execution
Summary
A heap-based buffer overflow in Microsoft Office Excel allows an unauthenticated remote attacker to execute code over a network. The attack requires the victim to take an action, such as opening a manipulated spreadsheet from an email or download. Microsoft rates the flaw as Important with a CVSS 3.1 base score of 8.8, and no active exploitation is known.
Affected
- Microsoft 365 Apps for Enterprise (32-bit and x64), from 16.0.1; the fixed build is not stated in the CVE data
- Office 365 for Mac, versions before 16.114.26101123
- Office LTSC 2021, versions before 16.0.14334.20974
- Office LTSC 2024, versions before 16.0.17932.21056 (not confirmed by Microsoft)
- Office LTSC for Mac 2021 and 2024, versions before 16.114.26101123
- Office Online Server, versions before 16.0.10417.20228 (not confirmed by Microsoft)
Fixed in
- Office 365 for Mac: 16.114.26101123
- Office LTSC 2021: 16.0.14334.20974
- Office LTSC for Mac 2021 and 2024: 16.114.26101123
- Office LTSC 2024: 16.0.17932.21056 (unverified, check the MSRC page)
- Office Online Server: 16.0.10417.20228 (unverified, see KB5002928)
- Microsoft 365 Apps: Unknown; check the October 2026 Excel update on the MSRC page
Workaround
- Unknown. No vendor workaround was found; patching is the available remediation.
Exploitation
- No known exploitation in the wild and no public proof of concept.
- MSRC: exploitation flag No, exploit code maturity Unproven.
- CISA SSVC: exploitation none, automatable no.
- Not found in the CISA KEV catalog in a limited search; verify on cisa.gov.
Our recommendation
- Deploy the October 2026 Office updates to all Windows and Mac clients.
- Confirm that Office Online Server is patched if it is deployed; prioritise internet-facing instances.
- Keep Protected View and macro restrictions enabled.
- Warn staff about spreadsheets from unknown senders or unexpected attachments.
- Verify the exact fixed builds on the MSRC page before rollout.
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
- MSRC advisory CVE-2026-97748 msrc.microsoft.com
- Microsoft 365 Apps security updates learn.microsoft.com
- Release notes Office for Mac learn.microsoft.com
- KB5002928 Office Online Server support.microsoft.com
- CNA data via Vulners vulners.com
- NVD record via OpenCVE 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, 17:35.
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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