Microsoft Word: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Word, part of Microsoft 365 Apps for Enterprise and Office LTSC 2021 and 2024, allows code execution. Microsoft rates it 7.8 (CVSS 3.1, local attack vector, user interaction required). An attacker would most likely need to trick a user into opening a crafted Word document, for example one delivered by phishing mail. Microsoft describes the attacker as unauthorized, but no network-exposed service is involved.
Affected
- Microsoft 365 Apps for Enterprise (32- and 64-bit)
- Microsoft Office LTSC 2021 (32- and 64-bit), versions 16.0.1 up to 16.0.14334.20974
- Microsoft Office LTSC 2024 (32- and 64-bit), versions 16.0.0 up to 16.0.17932.21056
Fixed in
- Microsoft Office LTSC 2021: 16.0.14334.20974 or later (from third-party aggregators, verify against Microsoft)
- Microsoft Office LTSC 2024: 16.0.17932.21056 or later (from third-party aggregators, verify against Microsoft)
- Microsoft 365 Apps for Enterprise: Unknown. Check the Office security update release notes (October 13, 2026) at https://aka.ms/OfficeSecurityReleases for the build of your channel.
Workaround
Unknown. No vendor workaround could be confirmed. Patching is the documented remedy; check the FAQ section of the MSRC advisory for any mitigation text.
Exploitation
- No known exploitation: CISA SSVC data shows exploitation 'none' and automatable 'no', with total technical impact.
- Not listed in the CISA KEV catalog.
- Microsoft rates exploit code maturity as unproven (temporal score 6.8).
- No public proof of concept found in our research; this does not prove that none exists.
- EPSS score 0.00618 (CNNVD-derived record).
- CNNVD describes the issue as possibly network-exploitable and rates it 8.8; this conflicts with Microsoft's local vector.
Our recommendation
- Install the October 2026 Office security updates on all endpoints, including LTSC clients managed separately.
- Confirm the fixed build on each machine after patching.
- Keep Protected View enabled for files from the internet and filter risky attachments at the mail gateway.
- Treat as standard priority unless signs of targeted document phishing appear.
- Check the MSRC advisory for any additional mitigation guidance.
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 Response Center: CVE-2026-96996 msrc.microsoft.com
- Microsoft 365 Apps security updates learn.microsoft.com
- Strix: CVE-2026-96996 www.strix.ai
- OpenCVE: CVE-2026-96996 app.opencve.io
- Vulners CNNVD record CNNVD-2026-27327619 vulners.com
- Vulners CVE record CVE-2026-96996 vulners.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 2 Nov 2026, 00:35.
Original description (NVD)
Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code locally.
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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