Microsoft Office Word: Double free allowing remote code execution
Summary
Microsoft Office Word contains a double free weakness (CWE-415) that allows an unauthorized attacker to execute code over the network. According to CVSS, exploitation requires user interaction, such as opening a crafted document received by email or download. Microsoft rates exploit code maturity as Unproven, and no active exploitation or public proof of concept has been found.
Affected
- Microsoft 365 Apps for Enterprise (32- and 64-bit): 16.0.1 before the fixed build (build number unknown)
- Office LTSC 2021 (32- and 64-bit): 16.0.1 before 16.0.14334.21048
- Office LTSC 2024: 16.0.0 before 16.0.17932.21140 (unverified, secondary source)
- Office 365 for Mac: 1.0.0 before 16.115.26110837
- Office LTSC for Mac 2021 and 2024: before 16.115.26110837 (2024 entry from secondary source)
Fixed in
- Office LTSC 2021: 16.0.14334.21048
- Office 365 for Mac: 16.115.26110837
- Office LTSC for Mac 2021 and 2024: 16.115.26110837
- Office LTSC 2024: 16.0.17932.21140 (unverified)
- Microsoft 365 Apps for Enterprise: Unknown. Check Microsoft's Office security release page.
Workaround
Unknown. No Microsoft workaround was found; apply the November 2026 updates.
- General hardening, not verified against the advisory: keep Protected View enabled for internet and email files, and restrict untrusted Office file types through file-block policy.
Exploitation
- Microsoft rates exploit code maturity as Unproven (E:U in the CVSS vector).
- No exploitation in the wild found. The actively exploited November zero-day is an Outlook flaw, not this one.
- No public proof of concept found.
- CISA KEV: not found in a limited search; recheck before relying on this.
Our recommendation
- Install the November 2026 Office security updates on all endpoints with Office, with high priority.
- Confirm the exact fixed builds for Microsoft 365 Apps and LTSC 2024 in the MSRC advisory.
- Restrict or sandbox email attachments and downloaded documents, and instruct users not to open unexpected files.
- Monitor for exploitation and check the CISA KEV catalogue.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE Record CVE-2026-109503 (CVE.org) www.cve.org
- MSRC Security Update Guide: CVE-2026-109503 msrc.microsoft.com
- Zero Day Initiative: November 2026 Security Update Review www.zerodayinitiative.com
- Cybersecurity News: Microsoft November 2026 Patch Tuesday cybersecuritynews.com
- Strix.ai: CVE-2026-109503 (secondary, unverified versions) 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, 23:53.
Original description (NVD)
Double free 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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