Microsoft Office Word: Heap-based buffer overflow allows remote code execution
Summary
A heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network. The attack requires a user to open a crafted document, typically delivered by email or download, and high attack complexity applies. Successful exploitation could affect confidentiality, integrity and availability on the affected workstation.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 before the fixed build (exact build unknown, see MSRC)
- Office 365 for Mac: 1.0.0 before 16.115.26110837
- Office LTSC 2021: 16.0.1 before 16.0.14334.21048
- Office LTSC 2024: 16.0.0 before 16.0.17932.21140 (source: third-party aggregator)
- Office LTSC for Mac 2021 and 2024: before 16.115.26110837 (LTSC 2024 Mac row source: third-party aggregator)
- Office 2016, 2019 and retail Office 2021: Unknown.
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown. See Microsoft Office security release page (aka.ms/OfficeSecurityReleases) and MSRC.
- Office 365 for Mac and LTSC for Mac: 16.115.26110837 or later
- Office LTSC 2021: 16.0.14334.21048 or later
- Office LTSC 2024: 16.0.17932.21140 or later
Workaround
Unknown. No documented workaround was found. Apply the security update.
Exploitation
- Microsoft's CVSS temporal vector indicates exploit code maturity 'unproven' and vendor-confirmed status.
- No public proof of concept was found.
- Unknown whether this CVE is the one Microsoft reports as exploited in the wild in the November 2026 Patch Tuesday review.
- CISA KEV status was not checked.
Our recommendation
- Treat as high priority in the November 2026 Office update cycle.
- Confirm the fixed build for each Office channel on MSRC and apply the update to all Office installations.
- Verify the installed versions afterwards.
- Filter or sandbox Word attachments at the mail gateway and keep Protected View enabled.
- Re-check CISA KEV and MSRC exploitation status over the next few days.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Response Center advisory CVE-2026-109500 msrc.microsoft.com
- CVE Record CVE-2026-109500 (CNA: Microsoft) www.cve.org
- Strix CVE-2026-109500 (third-party aggregator) www.strix.ai
- Rapid7 Patch Tuesday review November 2026 www.rapid7.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 11 Nov 2026, 06:02.
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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