Microsoft 365 Apps: Heap-based buffer overflow in Word allows code execution
Summary
Microsoft Word in Microsoft 365 Apps and Office LTSC editions contains a heap-based buffer overflow (CWE-122). A remote attacker can execute code on the affected system by getting a user to open or interact with a crafted document, for example one delivered by email or file sharing. The CVSS base score is 8.8, with high impact on confidentiality, integrity and availability.
Affected
- Microsoft 365 Apps for Enterprise: version 16.0.1 up to the fixed build (exact build to be confirmed on the vendor page)
- Office 365 for Mac: versions before 16.114.26101123
- Office LTSC 2021: versions before 16.0.14334.20974
- Office LTSC 2024: versions before 16.0.17932.21056
- Office LTSC for Mac 2021: versions before 16.114.26101123
- Office LTSC for Mac 2024: versions before 16.114.26101123
Fixed in
- Microsoft has published a fix. The fixed builds listed above are the upper bounds of the affected ranges in the CVE record and have not been independently verified.
- Confirm the exact fixed builds on the MSRC update guide page and the Microsoft Office security release page.
Workaround
- No vendor-published workaround is known.
Exploitation
- No public exploitation and no CISA KEV listing found at the time of research.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- No public proof-of-concept found. This does not prove that none exists.
Our recommendation
- Install the Microsoft 365 and Office security updates on all affected clients as soon as possible, prioritising systems that handle external documents.
- Verify installed build numbers against the fixed versions on the vendor page.
- Monitor email gateways for suspicious Word attachments and restrict macros and active content from untrusted sources.
- Watch for updates to the KEV catalogue and the vendor advisory.
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-2026-88202 msrc.microsoft.com
- Microsoft Office for Mac release notes learn.microsoft.com
- OpenCVE: CVE-2026-88202 app.opencve.io
- VulDB: CVE-2026-88202 vuldb.com
- Vulners CVE list: CVE-2026-88202 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 31 Oct 2026, 18:02.
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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