Microsoft Office Word: Use-after-free allows remote code execution
Summary
Microsoft Office Word contains a use-after-free memory flaw (CWE-416) in Microsoft 365 Apps, Office LTSC 2021 and 2024, and Office for Mac. An unauthorized attacker can execute code over a network. Per CVSS, exploitation needs high attack complexity and user interaction, so a victim must typically open a crafted document received by email or download.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 to before the build in the release notes at https://aka.ms/OfficeSecurityReleases\n- Office 365 for Mac: 1.0.0 to before 16.115.26110837\n- Office LTSC 2021: 16.0.1 to before 16.0.14334.21048\n- Office LTSC 2024: 16.0.0 to before 16.0.17932.21140\n- Office LTSC for Mac 2021 and 2024: 16.0.0 or 16.0.1 to before 16.115.26110837
Fixed in
- Office LTSC 2021: 16.0.14334.21048\n- Office LTSC 2024: 16.0.17932.21140\n- Office 365 for Mac and Office LTSC for Mac: 16.115.26110837\n- Microsoft 365 Apps for Enterprise: Unknown (build listed on the release notes page, not verified)
Workaround
Unknown. No workaround is documented in the sources reviewed. Apply the security update.
Exploitation
- No evidence of exploitation in the wild for this CVE in the sources reviewed.\n- CISA SSVC: exploitation none, not automatable, total technical impact.\n- Not listed in CISA KEV in the sources reviewed.\n- The actively exploited zero-day in the same release is an Outlook flaw, not this Word flaw.
Our recommendation
- Patch Microsoft 365 Apps and Office LTSC/Mac clients this week through the normal update channels.\n- Confirm that Microsoft 365 update channels are not paused.\n- Prioritise staff who regularly open external documents.\n- Check that email gateways filter or sandbox Office attachments.\n- Re-check the MSRC advisory and CISA KEV in the coming days.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE.org record CVE-2026-109491 www.cve.org
- MSRC Security Update Guide CVE-2026-109491 msrc.microsoft.com
- Strix CVE-2026-109491 (third-party NVD mirror) www.strix.ai
- Rapid7 November 2026 Patch Tuesday review www.rapid7.com
- Cybersecurity News: Microsoft November 2026 Patch Tuesday cybersecuritynews.com
- Action1 Patch Tuesday November 2026 www.action1.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 11 Nov 2026, 06:05.
Original description (NVD)
Use after 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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