Microsoft Office Excel: Remote code execution via double free
Summary
A double free memory corruption flaw in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. Exploitation requires a user to interact with the attack, most likely by opening a crafted Office file. Successful exploitation would give the attacker high impact on confidentiality, integrity and availability on the affected system.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (see Office security release page)
- Office 365 for Mac: 1.0.0 before 16.115.26110837
- Office LTSC 2021: 16.0.1 before 16.0.14334.21048
- Office LTSC 2024: 16.0.0 before 16.0.17932.21140 (secondary sources; not vendor-confirmed in our research)
- Office LTSC for Mac 2021 and 2024: before 16.115.26110837 (secondary sources; not vendor-confirmed in our research)
- Office Online Server: before 16.0.10417.20236 (secondary sources; not vendor-confirmed in our research)
Fixed in
- Fixes are included in the November 2026 Microsoft security updates for Office.
- Office LTSC 2021: 16.0.14334.21048 or later
- Office 365 for Mac and LTSC for Mac: 16.115.26110837 or later
- Microsoft 365 Apps for Enterprise: fixed build unknown; check the Office security release page
- Office Online Server: KB 5002946 (per secondary source)
Workaround
- Unknown. No vendor-documented interim mitigation was found; applying the security update is the fix.
Exploitation
- No evidence of exploitation in the wild, public proof of concept or CISA KEV listing was found at the time of research. This is not conclusive.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- NVD analysis is still pending, so the score may change.
Our recommendation
- Deploy the November 2026 Office security updates on all Microsoft 365, LTSC and Mac installations as a priority within the regular patch cycle.
- Keep Microsoft 365 auto-update enabled and verify the installed build.
- Check whether Office Online Server is in use and whether it is reachable from the internet; patch it if so.
- Filter email attachments and downloaded Office files, and restrict macros and opening documents from untrusted sources.
- Monitor for exploitation reports and raise the priority if exploitation is confirmed.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Critical
- Impact
- Remote code execution – Microsoft Office Excel
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Microsoft Office
- Updates (KB)
- KB5002946
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE Record CVE-2026-118296 www.cve.org
- Microsoft Security Update Guide msrc.microsoft.com
- Cybersecuritynews: Microsoft November 2026 Patch Tuesday cybersecuritynews.com
- Stefan Gossner blog: November 2026 PU blog.stefan-gossner.com
- Strix AI: CVE-2026-118296 www.strix.ai
- ThreatInt: CVE-2026-118296 cve.threatint.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, 22:02.
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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