Microsoft Office Word: Remote Code Execution due to off-by-one error
Summary
A off-by-one error (CWE-193) in Microsoft Office Word allows remote code execution. Microsoft 365 Apps, Office LTSC 2021 and 2024 and Office for Mac are affected according to the CNA data. An unauthenticated attacker can exploit it over the network if a user opens a crafted document, for example one received by email or downloaded from the web. Successful exploitation would give the attacker full impact on confidentiality, integrity and availability of the affected system.
Affected
- Microsoft 365 Apps for Enterprise: from 16.0.1 (upper bound only referenced via aka.ms/OfficeSecurityReleases in the CNA data)
- Office 365 for Mac: from 1.0.0 before 16.114.26101123
- Office LTSC 2021: from 16.0.1 before 16.0.14334.20974
- Office LTSC 2024: from 16.0.0 before 16.0.17932.21056
- Office LTSC for Mac 2021 and 2024: before 16.114.26101123
Fixed in
- Office LTSC 2021: 16.0.14334.20974
- Office LTSC 2024: 16.0.17932.21056
- Office for Mac and Office LTSC for Mac 2021/2024: 16.114.26101123
- Microsoft 365 Apps for Enterprise: Unknown (see MSRC advisory)
Workaround
Unknown.
Exploitation
- No public proof of concept or exploit found at the time of research.
- Not listed in CISA KEV.
- CISA SSVC: exploitation none, automatable no, technical impact total.
Our recommendation
- Check the MSRC advisory for the exact fixed build of each product.
- Inventory all Office installations, including Mac and LTSC systems, and confirm the installed build.
- Install the Microsoft update or the fixed LTSC build as a priority, starting with users who handle external documents.
- Restrict opening of documents from untrusted email and downloads.
- Monitor CISA KEV and the MSRC page for changes.
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-2026-108443) msrc.microsoft.com
- OpenCVE: CVE-2026-108443 app.opencve.io
- Strix: CVE-2026-108443 www.strix.ai
- threatint: CVE-2026-108443 cve.threatint.com
- Vulners: PT-2026-115245 vulners.com
- Offseq Radar: CVE-2026-108443 radar.offseq.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, 16:23.
Original description (NVD)
Off-by-one error 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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