Microsoft Office Word: Heap-based buffer overflow allows remote code execution
Summary
Microsoft Office Word contains a heap-based buffer overflow (CWE-122) that allows an unauthorized attacker to execute code over a network. The attacker needs no privileges, but a user must open a manipulated document, typically received by email or downloaded. Successful exploitation would give the attacker code execution in the context of the user, with high impact on confidentiality, integrity and availability.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build listed at aka.ms/OfficeSecurityReleases (exact build unknown)
- Office 365 for Mac: before 16.115.26110837
- Office LTSC 2021: before 16.0.14334.21048
- Office LTSC 2024: before 16.0.17932.21140 (third-party source only, verify on MSRC)
- Office LTSC for Mac 2021 and 2024: before 16.115.26110837 (third-party source only, verify on MSRC)
Fixed in
- Office LTSC 2021: 16.0.14334.21048
- Office 365 for Mac and Office LTSC for Mac: 16.115.26110837
- Microsoft 365 Apps for Enterprise: build listed at aka.ms/OfficeSecurityReleases (not stated in the CVE record)
- Office LTSC 2024: 16.0.17932.21140 (unverified)
Workaround
- Unknown.
- Until patched, keep Protected View enabled for documents from the internet and email.
- Restrict or sandbox attachments from unknown senders.
Exploitation
- No evidence of in-the-wild exploitation or public proof of concept found.
- Not listed in the CISA KEV catalog as far as known.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- Treat as nothing known for now, not as confirmed not exploited.
Our recommendation
- Check the Office build on all endpoints and servers against the fixed builds on the MSRC page.
- Deploy the November 2026 Office updates, prioritizing internet- and email-facing user machines.
- Patch related same-day Office CVEs in the same cycle.
- Keep Protected View enabled and check your mail gateway for Office attachments.
- Recheck CISA KEV, NVD and the MSRC page in the coming days, as the record is new.
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 Update Guide: CVE-2026-116923 msrc.microsoft.com
- CVE.org CVE Record: CVE-2026-116923 www.cve.org
- CWE-122: Heap-based Buffer Overflow cwe.mitre.org
- Strix: CVE-2026-116923 (third-party, unverified) www.strix.ai
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 10 Nov 2026, 22:38.
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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