Microsoft Office: Heap-based buffer overflow allows remote code execution
Summary
A heap-based buffer overflow in Microsoft Office allows remote code execution. Microsoft rates it Important with CVSS 8.8. An attacker must convince a user to open a malicious Office file, typically delivered by email or download. Microsoft reports no known exploitation.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 to before the build listed in the Microsoft advisory (Unknown.)
- Microsoft Office 365 for Mac: 1.0.0 to before 16.114.26101123
- Microsoft Office LTSC 2021: 16.0.1 to before 16.0.14334.20974 (unverified)
- Microsoft Office LTSC 2024: 16.0.0 to before 16.0.17932.21056 (unverified)
- Microsoft Office LTSC for Mac 2021 and 2024: before 16.114.26101123
Fixed in
- Security update released on October 13, 2026 (per Microsoft)
- Microsoft 365 Apps: fixed build Unknown; check the Microsoft Security Update Guide
- Office LTSC 2021 and 2024 (Windows): builds above are third-party data and must be verified against the MSRC table
- Office for Mac: Microsoft's FAQ says the LTSC for Mac updates were not immediately available; check MSRC for current status
Workaround
Unknown. No workaround or specific mitigation is documented by Microsoft in the sources reviewed.
Exploitation
- Microsoft: not exploited
- CISA: not in KEV; SSVC exploitation "none", automatable "no"
- EPSS: below 1%
- No public proof of concept found
- Exploitation requires user interaction (opening a malicious file)
Our recommendation
- Confirm that Microsoft 365 Apps (Click-to-Run channel) has received the October 2026 update and check the build against the MSRC table
- For Office LTSC 2021 and 2024 on Windows, verify the build is at or above the fixed build
- For Office on Mac, check MSRC for current update availability
- Keep attachment filtering, Protected View and macro restrictions enabled until verification is complete
- Make users aware of phishing with Office attachments
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-88197 msrc.microsoft.com
- Microsoft Office security updates (release notes) learn.microsoft.com
- Strix: CVE-2026-88197 (build numbers, unverified) www.strix.ai
- OpenCVE: CVE-2026-88197 app.opencve.io
- Microsoft 2026 CVE customer risk document cdn-dynmedia-1.microsoft.com
- Tenable plugin for October 2026 Office C2R update vulners.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, 18:00.
Original description (NVD)
Heap-based buffer overflow in Microsoft Office 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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