Microsoft 365 Apps: Remote code execution in Word via stack-based buffer overflow
Summary
A stack-based buffer overflow in Microsoft Word, part of Microsoft 365 Apps, Office LTSC and Office for Mac, allows an attacker to execute code over a network. The attacker needs no privileges, but a victim must open a crafted document, for example one received as an email attachment. The CVSS score is 8.8 (High). No exploitation or public proof of concept is known.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fix (exact fixed build unknown)
- Office 365 for Mac: 1.0.0 up to 16.114.26101123 (exclusive)
- Office LTSC 2021: 16.0.1 up to 16.0.14334.20974 (exclusive)
- Office LTSC 2024: 16.0.0 up to 16.0.17932.21056 (exclusive)
- Office LTSC for Mac 2021: 16.0.1 up to 16.114.26101123 (exclusive)
- Office LTSC for Mac 2024: 16.0.0 up to 16.114.26101123 (exclusive)
Fixed in
- Office LTSC 2021: 16.0.14334.20974
- Office LTSC 2024: 16.0.17932.21056
- Office 365 for Mac and Office LTSC for Mac: 16.114.26101123
- Microsoft 365 Apps for Enterprise: Unknown. See https://aka.ms/OfficeSecurityReleases and verify on MSRC.
Workaround
Unknown. No vendor-published workaround was found in the sources reviewed. Interim measures (not from the vendor): keep Protected View enabled, block or quarantine unexpected Word attachments at the mail gateway, and limit macros and external content.
Exploitation
- Not known to be exploited in the wild.
- CISA SSVC (Vulnrichment): exploitation none, automatable no.
- Not listed in CISA KEV in the latest records found.
- EPSS score: unknown.
- Public proof of concept: none known.
Our recommendation
- Read the MSRC advisory and confirm the fixed build for each update channel.
- Deploy the Microsoft 365 / Office update on all endpoints with Word, prioritising mail-facing users and finance and HR staff.
- Confirm that Protected View and macro restrictions are active and tighten attachment filtering.
- Re-check CISA KEV and exploit sources weekly for two to four weeks.
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-2026-108431 msrc.microsoft.com
- OpenCVE: CVE-2026-108431 app.opencve.io
- OffSeq Radar: CVE-2026-108431 radar.offseq.com
- VulDB: CVE-2026-108431 vuldb.com
- GitHub: CVE-2026-108431 status notes (KEV, EPSS) github.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, 16:26.
Original description (NVD)
Stack-based buffer overflow in Microsoft Office Word 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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.