Microsoft Office Excel: Remote code execution via out-of-bounds write
Summary
An out-of-bounds write in Microsoft Excel, part of Microsoft Office and Microsoft 365 Apps, allows an unauthorized attacker to execute code over a network. The attack requires a user to act, for example by opening a malicious or downloaded spreadsheet, and no privileges are needed. The CVSS score is 8.8 (High) with a total impact on confidentiality, integrity and availability. Microsoft and CISA data show no known active exploitation and no public proof-of-concept exploit.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (exact build unknown from sources)
- Microsoft Office 365 for Mac: versions before 16.114.26101123
- Office LTSC 2021 (Windows): versions before 16.0.14334.20974
- Office LTSC 2024 (Windows): versions before 16.0.17932.21056 (unverified, third-party source)
- Office LTSC for Mac 2021 and 2024: versions before 16.114.26101123 (per CNA record, to be verified)
- Office Online Server: versions before 16.0.10417.20228 (unverified, third-party source)
Fixed in
- Office 365 for Mac: 16.114.26101123 (per CNA record, not yet confirmed on the vendor page)
- Office LTSC 2021 (Windows): 16.0.14334.20974 (per CNA record)
- Office LTSC 2024 (Windows): 16.0.17932.21056 (unverified)
- Office Online Server: 16.0.10417.20228 (unverified, see KB5002928)
- Microsoft 365 Apps for Enterprise: unknown, see https://aka.ms/OfficeSecurityReleases
- Office LTSC for Mac 2021/2024: unknown
Workaround
Unknown. No vendor-documented workaround was found. General hardening applies: keep Protected View enabled and restrict macros and external content for untrusted documents.
Exploitation
- Not listed in CISA KEV.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- Microsoft exploit code maturity: Unproven.
- No public PoC or active exploitation reported by secondary sources (not fully verifiable).
Our recommendation
- Install the October 13, 2026 Office security updates on all affected Microsoft 365, Office LTSC and Mac installations, and verify the fixed builds on the MSRC advisory.
- Plan to upgrade Office 2021 installations, as they will not receive further fixes after this release cycle.
- Prioritise users who regularly open external or emailed spreadsheets.
- Block or restrict macros and external content from untrusted sources and keep Protected View enabled.
- Monitor for suspicious Excel activity and unexpected child processes on workstations.
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-2026-97762 msrc.microsoft.com
- Microsoft 365 Apps security updates learn.microsoft.com
- Microsoft KB5002928 (Office Online Server) support.microsoft.com
- CVE record via vulners (CNA data) vulners.com
- CVE record via OpenCVE (KEV and SSVC status) app.opencve.io
- Action1 Patch Tuesday October 2026 www.action1.com
- ZDI October 2026 Security Update Review www.zerodayinitiative.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, 17:34.
Original description (NVD)
Out-of-bounds write 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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