Microsoft Office Word: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Office Word allows an unauthenticated remote attacker to execute code. Exploitation requires user interaction (UI:R), most likely by opening a crafted Word document received by email or download. The CVSS vector rates confidentiality, integrity and availability impact as high. CISA SSVC lists exploitation as none, and no public proof of concept was found in the sources reviewed.
Affected
- Microsoft 365 Apps for Enterprise: affected from 16.0.1; the fixed build is unknown from the sources reviewed (see MSRC advisory)
- Microsoft Office LTSC 2021: 16.0.1 before 16.0.14334.20974 (per aggregators; verify on MSRC)
- Microsoft Office LTSC 2024: 16.0.0 before 16.0.17932.21056 (per aggregators; verify on MSRC)
Fixed in
- Microsoft Office security update for Word that addresses CVE-2026-108429 (see MSRC advisory)
- Microsoft 365 Apps for Enterprise: Unknown.
- Office LTSC 2021: 16.0.14334.20974 or later (per aggregators; verify)
- Office LTSC 2024: 16.0.17932.21056 or later (per aggregators; verify)
Workaround
No workaround identified in the sources. Patching is the stated remedy. Check the MSRC page for any listed mitigations.
Exploitation
- CISA SSVC: exploitation none, automatable no
- Not listed in CISA KEV
- RedPacket Security: no exploitation known
- No public proof of concept found in the sources reviewed; this does not rule one out
- EPSS score: unknown
Our recommendation
- Deploy the Microsoft Office Word update as a priority via the Microsoft 365 Apps update channel, WSUS or Intune.
- Confirm the installed build on each endpoint against the MSRC table, including the Microsoft 365 Apps entry.
- Restrict or sandbox opening of documents from untrusted sources and warn users about unexpected attachments.
- Monitor for suspicious Word process activity and follow-on malware. Because no exploitation is known, standard patch SLAs should be sufficient.
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-2026-108429 msrc.microsoft.com
- OpenCVE: CVE-2026-108429 app.opencve.io
- Strix: CVE-2026-108429 www.strix.ai
- OffSeq Radar: CVE-2026-108429 radar.offseq.com
- RedPacket Security: CVE alert CVE-2026-108429 www.redpacketsecurity.com
- GitHub issue: CVE-2026-108429 (KEV status) github.com
- VulDB: CVE-2026-108429 vuldb.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, 16:25.
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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