Microsoft Office Excel: Remote code execution via use-after-free
Summary
A use-after-free memory corruption flaw in Microsoft Office Excel allows remote code execution. An unauthenticated attacker can trigger it over the network, but a user must open a malicious file or otherwise interact with it. Successful exploitation could give the attacker full control over the affected user's session, CVSS 8.8.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the build listed at aka.ms/OfficeSecurityReleases
- Office LTSC 2021: 16.0.1 to below 16.0.14334.20974
- Office LTSC 2024: 16.0.0 to below 16.0.17932.21056
- Office for Mac (365): 1.0.0 to below 16.114.26101123
- Office LTSC for Mac 2021 and 2024: versions below 16.114.26101123
- Office Online Server: 16.0.0.0 to below 16.0.10417.20228
Fixed in
- Office LTSC 2021: 16.0.14334.20974 (third-party data, verify on MSRC)
- Office LTSC 2024: 16.0.17932.21056 (third-party data, verify on MSRC)
- Office for Mac (365): 16.114.26101123 (CNA data)
- Microsoft 365 Apps for Enterprise: Unknown. Check MSRC.
- Office LTSC for Mac 2021 and 2024: Unknown. Microsoft stated at release that updates were not yet available.
- Office Online Server: 16.0.10417.20228 (third-party data, not verified against KB5002928)
Workaround
Unknown. No vendor-documented interim mitigation was found.
Exploitation
- No evidence of exploitation in the wild known at time of writing.
- Not listed in CISA KEV.
- No public proof of concept found.
- CISA SSVC: exploitation none, not automatable.
- Microsoft exploit maturity: Unproven.
Our recommendation
- Install the October 2026 Office security updates on Microsoft 365 Apps and LTSC systems now, and verify build numbers against the MSRC table.
- Track the fix for Office LTSC for Mac and the Office Online Server patch separately.
- Enable Protected View and block or sandbox risky Office attachments and downloads until patched.
- Train users not to open unexpected Excel files from unknown senders.
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 msrc.microsoft.com
- Microsoft KB5002928 (Office Online Server) support.microsoft.com
- Microsoft Excel hotfix KB5002934 support.microsoft.com
- Microsoft 365 Apps security updates learn.microsoft.com
- OpenCVE CVE-2026-97017 app.opencve.io
- Vulners CVE-2026-97017 vulners.com
- Office-Watch October 2026 Patch Tuesday office-watch.com
- Strix.ai CVE-2026-97017 www.strix.ai
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, 17:45.
Original description (NVD)
Use after 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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