Microsoft Office Excel: Remote code execution through double free
Summary
A double free and a NULL pointer dereference in Microsoft Office Excel allow remote code execution. An unauthenticated attacker can run code in the context of the user by sending a specially crafted Excel file, for example as an email attachment or download. Exploitation requires that the user opens the file, and Microsoft's CVSS rating is 8.8 (High). Microsoft 365 Apps, standalone Office releases and Office Online Server are affected.
Affected
- Microsoft 365 Apps for Enterprise (32-bit and x64): from 16.0.1 (exact fixed build unknown)
- Office 365 for Mac: before 16.114.26101123
- Office LTSC 2021: before 16.0.14334.20974
- Office LTSC 2024: before 16.0.17932.21056 (to be verified)
- Office LTSC for Mac 2021 and 2024: before 16.114.26101123 (LTSC for Mac 2021 fixed build unknown)
- Office Online Server: before 16.0.10417.20228
Fixed in
- Office LTSC 2021: 16.0.14334.20974
- Office LTSC 2024: 16.0.17932.21056 (not yet confirmed against MSRC)
- Office Online Server: 16.0.10417.20228
- Office 365 for Mac: 16.114.26101123
- Microsoft 365 Apps for Enterprise: unknown, see the Microsoft Office release page
Workaround
Unknown. No vendor-documented workaround was found. Install the security update as the primary fix.
Exploitation
- Not listed in CISA's KEV catalogue.
- CISA SSVC: exploitation none, automatable no.
- No public proof of concept or exploitation reports found as of the research date.
Our recommendation
- Install the October 2026 Office security updates on all endpoints and on Office Online Server.
- Confirm the installed build numbers against the MSRC advisory, especially for Microsoft 365 Apps and LTSC 2024.
- Keep Protected View and attachment blocking enabled and open Excel files from untrusted email or downloads only after review.
- Monitor for reports of exploitation, as this is a memory corruption flaw.
Information from Microsoft (Patch Tuesday October 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)
- KB5002928
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide msrc.microsoft.com
- Action1 vulnerability details www.action1.com
- OpenCVE CVE-2026-97767 app.opencve.io
- Vulners CNA record mirror vulners.com
- Microsoft Office Online Server hotfix bulletin support.microsoft.com
- Office for Mac release notes learn.microsoft.com
- Strix CVE-2026-97767 www.strix.ai
- Qualys Patch Tuesday October 2026 review blog.qualys.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, 17:25.
Original description (NVD)
Double free 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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