Microsoft Office Word: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Office Word allows an unauthenticated attacker to execute code on a vulnerable system over the network. Exploitation requires a user to open a specially crafted file, which is typically delivered by email or download. Microsoft rates the issue as Important with a CVSS 3.1 base score of 8.8.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the build listed in Microsoft's security release notes (https://aka.ms/OfficeSecurityReleases)
- Microsoft Office LTSC 2021: 16.0.1 before 16.0.14334.20974
- Microsoft Office LTSC 2024: 16.0.0 before 16.0.17932.21056
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown. The fixed build is not stated in the sources reviewed; check the Microsoft advisory.
- Microsoft Office LTSC 2021: 16.0.14334.20974 or later
- Microsoft Office LTSC 2024: 16.0.17932.21056 or later
Workaround
Unknown. No official workaround has been identified; installing the update is the remediation.
Exploitation
- Publicly disclosed: No
- Exploited in the wild: No
- CISA SSVC: exploitation none, automatable no, technical impact total
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- No public proof of concept found in a limited search
Our recommendation
- Install the Microsoft Office security update on all affected systems; prioritise Office LTSC 2021 and LTSC 2024 installations, which require manual deployment.
- For Microsoft 365 Apps, confirm that automatic updates are working and that the installed build is at or above the fixed build in the advisory.
- Keep Protected View enabled, block macros from the internet, and train staff to be cautious with unsolicited Word files.
- Check the Microsoft advisory for Mac information, as availability for macOS is not confirmed.
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-2026-108428 msrc.microsoft.com
- OpenCVE: CVE-2026-108428 app.opencve.io
- Windows Forum: CVE-2026-108428 Microsoft Office Word Remote Code Execution Vulnerability windowsforum.com
- ThreatInt CVE mirror: CVE-2026-108428 cve.threatint.com
- GitHub issue: CVE-2026-108428 (KEV status) 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, 16:24.
Original description (NVD)
Heap-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.
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