Microsoft Office Excel: Double free allows remote code execution
Summary
A double free vulnerability (CWE-415) in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. The attack requires a user to open a malicious workbook, for example one received by email or downloaded from the internet. The vendor-assigned CVSS v3.1 base score is 8.8 (High). No exploitation in the wild and no public proof of concept were found at the time of publication.
Affected
- Microsoft 365 Apps for Enterprise (32/64-bit): from 16.0.1, exact fixed build unknown
- Office LTSC 2021: from 16.0.1, before 16.0.14334.21048
- Office LTSC 2024: from 16.0.0, before 16.0.17932.21140
- Microsoft Office 365 for Mac: from 1.0.0, before 16.115.26110837
- Office LTSC for Mac 2021: from 16.0.1, before 16.115.26110837
- Office LTSC for Mac 2024: from 16.0.0, before 16.115.26110837
- Older versions such as Office 2016 and 2019: unknown
Fixed in
- Microsoft November 2026 security update cycle
- Office LTSC 2021: 16.0.14334.21048 or later
- Office LTSC 2024: 16.0.17932.21140 or later
- Office 365 for Mac and LTSC for Mac: 16.115.26110837 or later
- Microsoft 365 Apps for Enterprise: build unknown, check the release notes at https://aka.ms/OfficeSecurityReleases
Workaround
Unknown. No vendor-published workaround was found. Patching is the remedy.
Exploitation
- Exploited in the wild: no evidence found
- Public proof of concept: none found (not checked directly on GitHub or Exploit-DB)
- CISA SSVC: exploitation none, automatable no, technical impact total
- The exploited zero-day in the November 2026 release is a different flaw (CVE-2026-124194, Outlook)
Our recommendation
- Patch Office in the current November 2026 update cycle, starting with staff who regularly open external spreadsheets
- Verify the exact fixed build numbers in the MSRC advisory before rollout
- Check the Office versions in use, including Microsoft 365 Apps and LTSC installations
- Keep Protected View enabled for files from the internet and train staff to be cautious with unexpected workbook attachments
- Monitor for unusual Excel processes or outbound connections
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide msrc.microsoft.com
- CVE.org CNA record www.cve.org
- VulDB vuldb.com
- threatint mirror cve.threatint.com
- Strix mirror www.strix.ai
- Patch Tuesday coverage (Cybersecurity News) cybersecuritynews.com
- Patch Tuesday coverage (Tenable) www.tenable.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 10 Nov 2026, 22:01.
Original description (NVD)
Double free in Microsoft Office Excel 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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